OIL  FUEL 

FOR 

STEAM  BOILEES 


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BY    PROF.   AUGUSTUS    H.    GILL 

Or  THE  MASSACHUSETTS  INSTITUTE  OF   TECHNOLOGY 

ENGINE  ROOM  CHEMISTRY 

BY  HUBERT   E.   COLLINS 

BOILERS  KNOCKS  AND  KINKS 

SHAFT  GOVERNORS  PUMPS 

ERECTING  WORK  SHAFTING,    PULLEYS    AND 
PIPES  AND  PIPING  BELTING 

BY  CHARLES  J.  MASON 
ARITHMETIC  OF  THE  STEAM  BOILER 


BY  RUFUS  T.  STROHM 
OIL  FUEL  FOR  STEAM  BOILERS 


McGRAW-HILL  BOOK  COMPANY,  INC. 
239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 


OIL  FUEL 

FOR 

STEAM  BOILERS 


BY 

RUFUS  T.  STROHM 

ENGINEERING  TEXTBOOK   WRITER 
INTERNATIONAL  CORRESPONDENCE  SCHOOLS 


FIRST  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 
239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 
1914 


-ff 


<  o 


COPYRIGHT,  1914,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY,  INC. 


THE. MAPLE. PRESS. YORK. PA 


s 

'V 


PREFACE 

The  purpose  of  this  volume  is  to  describe,  in  clear  and 
simple  language,  the  principles  that  underlie  the  use  of 
oil  as  a  fuel  in  steam-boiler  practice;  the  form  and  action 
of  various  types  of  burners;  the  arrangement  of  furnaces 
for  burning  oil  under  different  kinds  of  boilers;  the  opera- 
tion of  such  accessories  as  pumps,  heaters,  and  clean- 
ing devices;  the  methods  of  storing  oil;  and  such  other 
matters  as  might  naturally  arise  in  connection  with  the 
purchase  and  use  of  oil  fuel. 

No  attempt  has  been  made  to  describe  the  use  of  oil 
in  locomqtive  or  marine  practice,  or  in  heating,  tempering 
and  hardening  furnaces,  because  these  applications  are 
so  extensive  as  to  deserve  individual  treatment.  In- 
stead, this  volume  is  confined  to  the  burning  of  oil  in  the 
furnaces  of  stationary  steam  boilers,  and  the  endeavor 
has  been  to  cover  the  ground  fully  and  thoroughly. 

No  claim  for  originality  is  made,  except  in  the  manner 
of  arranging  and  presenting  the  facts.  The  material  is 
a  compilation  of  the  available  information  on  the  sub- 
ject of  oil  burning,  and  was  obtained  from  catalogs  and 
from  various  technical  publications  issued  during  the 
past  ten  years.  The  greater  part  of  the  contents  of  this 
volume  appeared  as  a  series  of  articles  in  the  Electrical 
World  during  1913  and  1914. 

v 


VI  PREFACE 

The  author  takes  this  opportunity  to  thank  the  various 
manufacturers  who  furnished  catalogs  and  other  valu- 
able information  and  to  acknowledge  his  indebtedness 
to  the  publishers  of  the  Electrical  World  for  granting 
permission  to  reprint  the  series  of  articles  in  book  form. 

RUFUS  T.  STROHM. 
SCRANTON,  PA., 
May,  1914. 


CONTENTS 

PAGE 

PREFACE    v 

LIST  OF  ILLUSTRATIONS ix 

CHAPTER 

I.  PROPERTIES  OF  OIL  FUEL i 

II.  REQUIREMENTS     FOR     EFFICIENT    BURNING    OF     OIL 

FUEL 15 

III.  METHODS  OF  SPRAYING  OIL  FUEL 20 

IV.  BURNERS  FOR  OIL  FUEL 27 

V.  CLEANING  OF  OIL  FUEL 44 

VI.  PUMPING  AND  HEATING  OF  OIL  FUEL 54 

VII.  OIL-BURNING  FURNACES 65 

VIII.  INSTALLATION  OF  OIL  BURNERS 80 

IX.  STORAGE  OF  OIL  FUEL 89 

X.  COMBUSTION  OF  OIL  FUEL 102 

XI.  MANAGEMENT  OF  OIL-BURNING  PLANTS 108 

XII.  PURCHASE  OF  OIL  FUEL 117 

XIII.  ADVANTAGES  AND  DISADVANTAGES  OF  OIL  FUEL.   .    .  129 

XIV.  PERFORMANCES  OF  OIL-BURNING  BOILERS 136 

INDEX 141 


Vll 


ILLUSTRATIONS 

FIG.  PAGE 

1  Hydrometer  for  determining  density  of  oil    6 

2  Curve  showing  relation  of  specific  gravity  and  density 8 

3  Flame  of  wax  candle 16 

4  Atomizing  by  pressure  and  centrifugal  force  combined.  ...  22 

5-6  Principle  of  outside-mixing  burners 24 

7-8  Principle  of  projector  burner  and  inside-mixing  burner.  .  24 

9  Principle  of  injector  burner 25 

10  Regular  Gem  oil  burner 28 

1 1  Improved  Gem  oil  burner 29 

1 2  Parson  oil  burner 29 

13  Booth  oil  burner  with  pipe  connections 30 

14  Best  oil  burner : 32 

1 5  Hammel  oil  burner 34 

1 6  Piping  for  Hammel  burner 35 

17  Regular  Kirkwood  oil  burner 36 

18  Piping  for  Kirkwood  burner >37 

19  Koerting  centrifugal  spray  nozzle 38 

20  Kirkwood  burner  with  fixed  steam-to-oil  ratio 40 

21  Slot  oil  burner  with  renewable  disk 41 

22  Inside-mixing  slot  oil  burner 42 

23-24  Simple  oil  strainer  and  piping  for  strainer 46 

25-26  Suction-pipe  strainer  and  T-fitting  used  for  strainer 48 

27-28  Perforated  metal  strainer  and  basket  strainer  for  quick 

cleaning 49 

29  Koerting  type  of  oil  strainer 50 

30-31  Two  views  of  oil  strainer  arranged  for  cleaning  without 

removal 52 

32-33  Standpipe  used  to  obtain  steady  oil  pressure  and  safety 

device  for  draining  standpipe 55 

34  Oil-pressure  pump  with  heater 58 

35-36-37  Forms  of  oil  heaters 61 

ix 


X  ILLUSTRATIONS 

Fia.  PAGE 

38  Corrugated  counterflow  oil  heater 62 

39  Thermometer  for  finding  temperature  of  oil  in  pipe 64 

40  Return- tubular  boiler  with  slot  oil  burner 66 

41  Return-tubular  boiler  with  Kirkwood  oil  burner 67 

42  Return-tubular  boiler  with  Best  oil  burner 68 

43  Babcock  &  Wilcox  boiler  with  burner  at  front 69 

44  Babcock  &  Wilcox  boiler  with  burner  at  bridge  wall 71 

45  Heine  boiler  with  preheating  of  ak  supply 73 

46  Stirling  boiler  with  auxiliary  air  duct 74 

47  Stirling  boiler  with  burner  at  back  of  furnace 75 

48  Stirling  boiler  with  burner  set  high  at  front 76 

49  Coal-burning  boiler  with  oil  used  for  banking  and  peak 

loads 78 

50  Piping  for  Gem  oil  burner 80 

51  Piping  and  oil-regulating  cock  for  Best  burner 81 

52  Oil-regulating  cock 82 

53-54  Oil-regulating     valve    and    arrangement    for    finding 

amount  of  steam  used  by  burners 84 

55  Oil-storage  tank  with  connections 90 

56-57-58  Arrangement  for  emptying  tank  car;  simple  form 

of  vent  pipe;  vent  pipe  and  telltale 93 

59  Indicator  for  oil-storage  tank 96 

60  Section  of  oil  tester 120 

61  Lamp  of  tester  for  flash  point  of  oil 121 

62  Sampling  pipe 126 

63  Sampling  bottle  on  rod 126 


OIL  FUEL  FOR  STEAM  BOILERS 

CHAPTER  I 

PROPERTIES  OF  OIL  FUEL 

At  the  rate  at  which  oil  fuel  is  being  produced  at  the 
present  time,  there  is  no  danger  that  it  will  supplant  coal 
as  a  boiler  fuel,  except  in  a  few  localities.  For  if  all  the 
oil  produced  throughout  the  world  in  a  year  were  used  for 
the  purpose  of  steam  generation,  it  would  furnish  an 
amount  of  power  equal  to  only  about  one-thirtieth  of 
that  annually  required  by  the  power  and  manufacturing 
plants  of  the  globe.  Therefore,  unless  far  greater  oil 
fields  are  discovered  and  the  yearly  yield  of  the  wells  is 
enormously  increased,  there  is  no  danger  that  oil  will 
become  a  general  competitor  of  solid  fuel  in  steam-boiler 
plants. 

Nevertheless,  there  are  localities  in  which  oil  forms  a 
useful,  economical  and  desirable  fuel,  and  in  which  it  is 
used  to  the  exclusion  of  coal.  Such  localities  are  the 
regions  in  which  the  oil  is  produced.  Yet  there  are  oil 
fields  in  which  little  oil  is  used  for  steam-boiler  fuel,  be- 
cause of  the  fact  that  the  oil  is  more  valuable  for  other 
purposes.  Consequently,  the  factors  that  determine 
whether  oil  shall  be  used  for  fuel  in  preference  to  coal  are 
as  follows: 

1 


2  OIL  FUEL  FOR,  STEAM  BOILERS 

The  price  of  the  oil  must  be  low  enough  to  enable  it  to 
compete  with  coal  in  that  particular  neighborhood;  the 
supply  must  be  continuous  and  ample,  so  as  to  prevent 
shut-downs;  and  it  must  be  of  a  quality  that  can  be  used 
without  unusual  difficulties  in  the  furnace. 

In  the  United  States  the  greatest  oil  fields  are  located  in 
three  regions.  The  first  of  these  embraces  western 
Pennsylvania,  Ohio  and  West  Virginia.  The  second 
includes  portions  of  Texas,  Louisiana  and  Oklahoma. 
The  third  is  in  southern  California.  The  oil  that  is 
produced  in  the  first  of  these  regions,  however,  is  not 
used  to  any  great  extent  as  a  fuel  for  steam  boilers,  for 
the  simple  reason  that  it  is  of  such  quality  and  composi- 
tion that  it  is  more  valuable  for  refining.  Also,  this  same 
region  contains  great  deposits  of  bituminous  coal,  so  that 
it  is  more  economical  to  use  this  solid  fuel  for  power 
plants. 

The  oil  produced  in  the  second  and  third  fields  named 
above  is  also  used  in  refineries,  but  a  moderate  proportion 
is  employed  for  fuel  in  boiler  furnaces.  The  reason  lies 
in  the  fact  that  coal  is  scarce  in  either  of  these  fields. 
That  is,  all  coal  used  in  these  districts  must  be  brought 
by  rail  or  water  from  some  distant  point  or  points,  with 
the  natural  result  that  the  cost  per  ton  is  greatly  in- 
creased. Because  of  this  fact,  it  is  far  cheaper  to  use  oil 
as  the  fuel,  as  it  is  found  in  the  immediate  vicinity  and 
does  not  need  to  be  transported  over  such  great  distances. 

The  oils  that  are  used  for  fuel  are  forms  of  petroleum, 
which  is  the  term  that  includes  all  the  mineral  oils  derived 
from  the  earth.  The  characteristics  of  petroleum,  such 
as  color,  density  and  odor,  vary  according  to  the  region 


PROPERTIES  OF  OIL  FUEL  3 

in  which  the  oil  is  obtained.  In  some  parts  of  the  world 
petroleum  is  clear  and  without  color,  like  water,  and  in 
other  parts  of  the  world  it  is  black.  The  petroleum  found 
in  the  United  States  is  brown  or  reddish  brown  in  color, 
as  a  rule,  when  in  a  tank  or  other  vessel.  But  if  a  sample 
is  poured  into  a  glass  or  a  bottle  and  is  then  held  up  so 
that  the  light  can  pass  through  it,  the  oil  will  appear  to 
have  a  dark  green  color. 

In  spite  of  the  differences  in  color  and  other  character- 
istics, however,  all  petroleums  are  very  much  alike  in 
composition;  that  is,  they  are  all  liquid  hydrocarbons. 
The  principal  elements  of  which  they  are  composed,  and 
which  make  them  valuable  as  fuel,  are  about  the  same  as 
those  in  coal,  namely,  carbon  and  hydrogen;  also,  like 
coal,  petroleum  contains  oxygen,  nitrogen  and  moisture. 
The  relative  percentages  of  these  constituents  vary  some- 
what according  to  the  locality  from  which  the  oil  is  de- 
rived. For  example,  an  average  Texas  petroleum  has 
84.6  per  cent,  of  carbon,  10.9  per  cent,  of  hydrogen, 
1.6  per  cent,  of  sulphur  and  2.9  per  cent,  of  oxygen.  A 
sample  of  California  petroleum,  on  the  other  hand, 
contains  85  per  cent,  of  carbon,  12  per  cent,  of  hydrogen, 
0.8  per  cent,  of  sulphur,  i  per  cent,  of  oxygen,  0.2  per 
cent,  of  nitrogen  and  i  per  cent,  of  moisture.  Thus, 
petroleum  may  be  taken  as  having  from  83  to  87  per  cent, 
of  carbon,  from  10  to  16  per  cent,  of  hydrogen,  and  trifling 
percentages  of  sulphur,  oxygen  and  nitrogen.  Those  oils 
that  contain  sulphur  usually  have  a  disagreeable  smell, 
due  to  the  presence  of  the  sulphur. 

Although  all  oil  used  for  fuel  is  derived  primarily  from 
petroleum,  it  may  be  obtained  commercially  in  either  of 


-   4 .  OIL  FUEL  FOR  STEAM  BOILERS 

two  forms,  namely,  crude  oil  and  fuel  oil.  Crude  oil  is 
simply  raw  petroleum,  in  the  condition  in  which  it  is 
obtained  from  the  oil  well,  and  is  not  subjected  to  any 
treatment.  Fuel  oil,  on  the  other  hand,  is  a  residue; 
that  is,  it  is  the  oil  that  remains  when  petroleum  is  sub- 
jected to  a  partial  distillation. 

The  distillation  process  just  referred  to  drives  off  the 
lighter  oils  contained  in  petroleum  and  leaves  the  heavier 
ones.  The  crude  oil  is  put  in  closed  tanks  called  stills  and 
is  slowly  heated.  Now,  the  crude  oil  consists  of  a  mix- 
ture of  a  large  number  of  liquid  hydrocarbons  having 
different  densities  and  boiling  points.  Consequently,  as 
the  temperature  in  the  still  rises,  these  various  oils  are 
brought  to  the  boiling  point,  one  after  another,  and  escape 
from  the  still  in  the  form  of  vapor.  The  vapor  is  led 
through  pipe  coils  and  is  chilled,  whereupon  it  condenses 
and  becomes  liquid  again. 

At  first,  while  the  temperature  rises  from  about  100  deg. 
Fahr.  to  160  deg.  Fahr.,  petroleum  ether  will  be  boiled 
off,  this  being  a  very  light  oil.  From  a  temperature  of 
1 60  deg.  Fahr.  to  about  175  deg.  Fahr.  gasoline  will  be 
distilled.  Naphtha  will  be  driven  off  while  the  tempera- 
ture changes  from  about  175  deg.  Fahr.  to  about  300  deg. 
Fahr.,  and  from  300  deg.  Fahr.  to  570  deg.  Fahr.  the  oil 
driven  off  will  be  what  is  commercially  known  as  kero- 
sene. The  oil  that  remains  in  the  still  after  the  tempera- 
ture has  reached  570  deg.  Fahr.  consists  of  lubricating 
oils,  paraffin  and  coke  or  asphalt.  The  crude  oils  found 
in  the  region  of  western  Pennsylvania  have  a  coke  base, 
whereas  those  from  Texas  and  California  have  an  asphalt 
base. 


PROPERTIES  OF  OIL  FUEL  5 

The  residue,  or  oil  remaining  in  the  still  after  the 
petroleum  ether,  gasoline,  benzine  and  kerosene  have 
been  distilled,  is  what  is  frequently  used  as  fuel  for  steam 
boilers  and  sold  under  the  name  of  fuel  oil.  It  is  simply 
the  oil  remaining  after  the  lighter  oils  have  been  driven 
off  from  the  crude  petroleum.  The  effect  of  the  heating 
and  driving  off  of  the  lighter  constituents  is  to  leave  a 
residue  that  weighs  more  per  cubic  foot  than  the  original 
petroleum ;  in  other  words,  the  density  of  fuel  oil  is  greater 
than  that  of  the  crude  oil  from  which  it  is  obtained. 
Moreover,  the  distilling  process  causes  a  change  in  the 
composition  of  the  oil.  The  percentages  of  carbon  and 
sulphur  are  decreased  slightly  and  those  of  hydrogen  and 
oxygen  are  increased. 

As  the  constituents  of  liquid  fuel  are  the  same  as  those  of 
coal,  the  same  formula  may  be  used  to  calculate  the  heat 
values,  or  calorific  values,  of  the  two  kinds  of  fuel;  that  is, 

Q  =  14,600  C+  62,000  (  H  —    j  +  4,000  S 

in  which  Q  =  calorific  value,  in  heat -units  per  pound; 

C  =  percentage  of  carbon,  expressed  decimally; 
H  =  percentage  of  hydrogen,  expressed  deci- 
mally ; 

O  =  percentage  of  oxygen,  expressed  decimally; 

5  =  percentage  of  sulphur,  expressed  decimally. 

Thus,  if  a  fuel  oil  has  83.3  per  cent,  of  carbon,  12.5  per 

cent,  of  hydrogen,  0.5  per  cent,  of  sulphur  and  3.7  per 

cent,  of  oxygen  its  theoretical  calorific  value  is 

Q  =  14,600  X  0.833  +  62,000(0.125—    -/— )  +  4,000  X 

\  o     / 

0.005  =  TQj645  heat  units. 


6 


OIL  FUEL  FOR  STEAM  BOILERS 


This,  it  must  be  remembered,  is  but  the  approximate 
heat  value,  based  on  the  chemical  composition  of  the  oil. 
A  more  reliable  estimate  of  the  heat  value  may  be  ob- 
tained by  making  a  calorimetric  test  of  a  sample  of  the 
fuel  oil. 

The  calorific  values  of  oils  vary  according  to  the  locali- 
ties from  which  they  are  derived  and  range  from  about 
17,000  to  21,000  heat  units  per  pound. 
The  Texas  and  California  crude  oils  used 
in  power-plant  work  seem  to  have  a 
calorific  value  averaging  about  18,600 
heat  units  per  pound. 

Fuel  oil  and  crude  oil  are  usually  not 
quite  so  heavy  as  water,  bulk  for  bulk; 
that  is,  the  specific  gravity  of  oil  is  ordi- 
narily less  than  that  of  water.  As  a  general 
rule,  however,  in  the  purchase  and  sale  of 
oil  fuel  the  specific  gravity  is  not  directly 
mentioned;  instead,  it  is  implied  by  stat- 
ing the  density  in  degrees  Baume,  or  the 
reading  of  a  Baume  hydrometer  allowed 
to  float  in  the  oil. 

The  method  of  determining  the  density 
of  an  oil  by  means  of  the  Lydrometer  is 
shown  in  Fig.  i.  A  sample  of  the  oil  is  put  into  the 
deep  glass  a,  and  the  hydrometer  is  lowered  into 
the  oil,  in  which  it  will  float  and  soon  come  to  rest. 
The  hydrometer  consists  of  a  glass  tube  b,  at  the 
lower  end  of  which  are  the  chamber  c  and  the  bulb  d. 
The  large  part  c  is  filled  with  air,  and  the  bulb  d 
is  filled  with  quicksilver.  The  former  causes  the 


FIG.  i. — 
H  y  d  r  o  m  eter 
for  determin- 
ing density  of 
oil. 


PROPERTIES  OF  OIL  FUEL  7 

hydrometer   to   float,    and   the    latter   keeps   it   in   an 
upright  position. 

The  stem  b  is  graduated  with  a  series  of  divisions,  the 
lowest  one  being  marked  10.  When  the  hydrometer  is 
put  in  a  vessel  of  pure  distilled  water,  it  sinks  until  the 
graduation  marked  10  is  even  with  the  surface  of  the 
water.  In  other  words,  10  deg.  Baume,  or  10  deg.  B., 
as  it  is  usually  abbreviated,  corresponds  to  a  specific 
gravity  of  i,  or  the  specific  gravity  of  pure  water. 

When  the  hydrometer  is  put  into  a  vessel  containing  oil 
that  is  lighter  than  water,  it  sinks  farther  than  it  did  in 
water,  and  some  other  graduation  greater  than  10  comes 
even  with  the  surface  of  the  oil.  The  number  of  this 
graduation  then  indicates  the  density  of  that  particular 
oil,  in  degrees  Baume.  For  example,  if  the  graduation 
marked  26  came  level  with  the  surface  of  the  oil,  the 
density  of  the  oil  would  be  26  deg.  Baume. 

If  the  density  of  an  oil  lighter  than  water  is  given  in 
degrees  Baume,  the  corresponding  specific  gravity  may 
be  found  by  using  the  formula 

140 


in  which  G  =  specific  gravity  of  oil; 

B  =  density,  in  degrees  Baume. 

For  instance,  if  an  oil  has  a  density  of  20  deg.  Baume 
its  specific  gravity  is 

~  140 


To  enable  the  specific  gravity  for  any  Baume  reading  to 
be  found  quickly,  without  any  calculations,  the  curve 


OIL  FUEL  FOR  STEAM  BOILERS 


CO         O         C\J 

r*.       ex)       oq 

AJ.IAVUO    OIJI03ds 


•<f         IO         00          O         O4 
03          00         00          <T>         <T> 


PROPERTIES  OF  OIL  FUEL  9 

shown  in  Fig.  2  is  given.  For  example,  suppose  that  it  is 
desired  to  find  the  specific  gravity  of  an  oil  having  a 
density  of  19  deg.  Baume.  On  the  horizontal  scale  locate 
the  division  corresponding  to  19,  which  is  the  first  vertical 
line  to  the  left  of  that  marked  20.  From  the  point  where 
this  vertical  line  meets  the  curve  follow  horizontally  to 
the  scale  at  the  left-hand  edge  of  the  diagram.  It  will 
meet  the  scale  at  a  point  that  corresponds  to  0.94.  This 
is  the  desired  specific  gravity.  In  other  words,  a  Baume 
reading  of  19  deg.  corresponds  to  a  specific  gravity  of  0.94. 

The  same  diagram  may  be  used  to  find  a  Baume  read- 
ing corresponding  to  a  given  specific  gravity,  by  reversing 
the  foregoing  method.  Suppose  that  it  is  desired  to  find 
the  Baume  reading  of  an  oil  having  a  specific  gravity  of 
0.91.  Having  located  the  point  corresponding  to  0.91, 
midway  between  0.90  and  0.92  on  the  left-hand  scale, 
follow  horizontally  to  the  curve  and  then  down  to  the 
bottom  scale.  The  point  thus  reached  will  be  at  the  first 
division  to  the  left  of  25,  corresponding  to  24.  Hence,  a 
specific  gravity  of  0.91  corresponds  to  a  Baume  reading  of 
24  deg. 

If  possible,  the  density  of  oil  should  be  determined  at 
a  temperature  of  60  deg.  Fahr.,  as  the  formula  and  the 
curve  will  give  the  correct  equivalent  specific  gravity 
only  under  this  condition;  however,  it  may  not  be  con- 
venient to  do  this  in  all  cases.  If  the  temperature  of 
the  oil  sample  is  greater  or  less  than  60  deg.  Fahr.,  it 
should  be  noted,  so  that  the  specific  gravity  correspond- 
ing to  the  Baume  reading  may  be  corrected  for  the  differ- 
ence in  temperature. 

A   higher   temperature   than    the   standard,    60    deg. 


10  OIL  FUEL  FOR  STEAM  BOILERS 

Fahr.,  causes  the  oil  to  expand,  and  the  specific  gravity 
calculated  from  the  Baume  reading  will  therefore  be  too 
low.  A  lower  temperature  than  60  deg.  Fahr.  will  cause 
the  oil  to  become  more  dense,  so  that  the  specific  gravity 
corresponding  to  the  Baume  reading  will  be  too  high. 

The  correction  amounts  to  0.0004  f°r  each  degree 
Fahrenheit.  That  is,  if  the  temperature  is  less  than  60 
deg.  Fahr.,  the  observed  specific  gravity  must  be  reduced 
by  an  amount  equal  to  0.0004  times  the  difference  be- 
tween the  observed  temperature  and  60  deg.  Fahr.;  and 
if  the  temperature  is  above  60  deg.  Fahr.,  the  observed 
specific  gravity  must  be  increased  by  an  amount  equal  to 
0.0004  times  the  difference  between  the  observed  tem- 
perature and  60  deg.  Fahr. 

To  illustrate,  suppose  that  a  sample  of  oil  is  tested  at 
a  temperature  of  46  deg.  Fahr.  and  found  to  have  a  den- 
sity of  30  deg.  Baume.  The  specific  gravity  corresponding 
to  this  reading  is  0.875  with  oil  at  60  deg.  Fahr.  But 
in  this  case  the  oil  has  a  temperature  14  deg.  lower  than 
the  standard.  Hence,  the  observed  specific  gravity, 
0.875,  must  be  reduced  by  0.0004  X  14  =  0.0056,  and 
the  corrected  specific  gravity  then  becomes  0.875  ~~ 
0.0056  =  0.8694,  which  is  the  true  specific  gravity  of  the 
oil. 

Again,  suppose  that  at  a  temperature  of  80  deg.  Fahr. 
an  oil  showed  a  density  of  25  deg.  Baume,  equivalent  to 
a  specific  gravity  of  0.9032.  As  the  temperature  of  the 
sample  is  20  deg.  in  excess  of  the  standard,  the  observed 
specific  gravity  must  be  increased  by  0.0004X20  = 
0.0080,  giving  a  corrected  value  of  0.9032  +  0.0080  = 
0.9112. 


PROPERTIES  OF  OIL  FUEL  11 

Particulars  as  to  the  flash  point,  firing  point,  specific 
gravity,  and  calorific  value  of  various  American  oils  are 
given  in  Table  I.  These  values  are  taken  from  a  table 
published  in  the  Iowa  Engineer  of  October,  1905,  and 
cover  the  main  oil  fieMs  of  the  United  States,  with  the 
exception  of  Ohio.  The  calorific  values  were  obtained 
by  tests  made  with  a  Parr  calorimeter.  It  may  be  noted 
that  the  calorific  values  of  crude  oils  from  any  particular 
district  vary  but  little.  The  reduced  oils,  or  those  from 
which  some  of  the  lighter  constituents  were  removed, 
gained  in  specific  gravity  and  did  not  lose  in  calorific 
value;  also,  the  flash  point  was  raised  considerably.  In 
a  number  of  cases,  double  sets  of  values  are  given.  These 
are  the  results  of  tests  on  samples  obtained  from  different 
companies  in  the  same  field. 

Table  II  is  given  because  it  is  a  summary  of  a  large 
number  of  tests  made  on  the  petroleums  of  the  San 
Joaquin  Valley,  California,  by  the  Government  Bureau 
of  Mines.  The  detailed  report  of  the  tests  is  contained 
in  Bulletin  19.  The  composite  samples  referred  to  in  the 
table  were  made  up  by  taking  equal  weights  of  all 
the  samples  from  a  given  locality  and  mixing  them.  For 
example,  the  composite  sample  of  Kern  River  oil  was 
made  up  of  30  grams  from  each  of  the  40  samples  previ- 
ously tested. 


12 


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CHAPTER  II 
REQUIREMENTS  FOR  EFFICIENT  BURNING  OF  OIL  FUEL 

The  first  essential  for  the  successful  burning  of  crude  oil 
or  fuel  oil  is  that  it  must  be  atomized  or  broken  up  into  a 
fine  spray  or  mist;  next,  it  must  be  thoroughly  mixed  with 
a  sufficient  amount  of  air  to  insure  its  complete  combus- 
tion; and,  finally,  the  combustion  must  take  place  in  a 
furnace  of  suitable  size  and  shape.  These  three  require- 
ments must  be  met  in  every  power  plant  in  which  liquid 
fuel  is  to  be  used. 

When  crude  oil  was  first  tried  as  a  fuel  for  steam  boilers, 
attempts  were  made  to  burn  it  by  running  it  into  shallow 
pans  and  igniting  its  surface.  This  was  simply  following 
the  old  methods  applied  in  the  case  of  coal.  For,  as  the 
coal  was  spread  out  in  the  form  of  a  bed  of  fairly  uniform 
thickness  on  the  grates,  so  was  the  oil  spread  out  in  a 
shallow  sheet.  This  method,  however,  was  wholly  un- 
satisfactory and  unsuccessful  and  was  soon  abandoned. 
The  reason  for  its  failure  was  that  oil  differs  so  greatly 
from  coal. 

With  coal  the  effect  of  the  heat  is  to  drive  off  the  vola- 
tile matter  in  the  form  of  gases,  which,  mixing  with  the  air 
passing  through  the  bed  of  fuel,  burn  and  generate  suffi- 
cient heat  to  ignite  the  solid  carbon  remaining  on  the 
grates.  This  bed  of  burning  carbon  then  furnishes  the 
heat  required  to  ignite  succeeding  charges  of  fresh  fuel. 

15 


16 


OIL  FUEL  FOR  STEAM  BOILERS 


With  oil,  there  is  no  incandescent  bed  of  fuel.  The  oil 
does  not  burn  in  the  liquid  form.  Before  it  can  burn  it 
must  be  changed  to  a  vapor,  or  volatilized,  and  this  is 
done  by  the  action  of  heat.  The  action  may  be  illustrated 
by  the  burning  of  a  common  wax  candle,  as  shown  in 

Fig.  3- 

When  the  wick  of  a  candle  is  lighted  the  heat  due  to  the 
burning  melts  some  of  the  wax  just  below  the  flame,  and 
the  melted  wax  is  at  once  carried  up  the 
wick  by  capillary  action.  As  it  comes 
closer  to  the  flame  it  grows  hotter  and 
hotter,  until  at  length  it  reaches  the  boil- 
ing point  and  passes  into  vapor.  This 
vapor  mixes  with  the  air  and  thus  forms 
a  combustible  mixture,  which  burns 
above  the  tip  of  the  wick.  Part  of  the 
heat  due  to  its  burning  is  used  to  melt 
and  vaporize  more  of  the  wax,  and  the 
burning  is  thus  rendered  a  continuous 
process. 

It  will  be  observed  that  the  flame  of  a 
candle  varies  in  color.  Just  around  the 
tip  of  the  wick  there  is  nothing  to  be 
seen.  This  transparent  section  a  is  the  vaporized  wax, 
before  it  has  had  a  chance  to  mix  with  air  and  burn. 
Around  this  is  another  transparent  section  b  that  has  a 
bluish  tinge.  Here  the  vapor  has  mixed  with  some  air 
and  is  being  partly  burned.  Farther  up,  there  is  more 
opportunity  for  the  mixing  of  a  sufficient  quantity  of  air, 
and  the  flame  there  becomes  yellow  or  yellowish  white. 
That  part  of  the  flame  that  is  tinged  with  blue  indicates 


FIG.     3. — Flame 
of  wax  candle. 


EFFICIENT  BURNING  OF  OIL  FUEL  17 

incomplete  combustion,  because  the  supply  of  oxygen  in 
the  air  that  mixes  with  the  vapor  is  not  sufficient  to  burn 
the  carbon  to  dioxide.  This  portion  of  the  flame  does 
not  have  so  high  a  temperature  as  the  yellowish  portion 
where  the  combustion  is  complete. 

As  a  further  experiment  to  show  that  the  crude  oil  will 
not  burn  in  the  liquid  form,  a  live  coal  or  a  blazing  stick 
may  be  dropped  or  thrust  into  a  vessel  containing  the  oil. 
Instead  of  firing  the  oil,  the  live  coal  will.be  quenched  or 
the  flame  of  the  stick  will  be  extinguished  by  the  oil,  for 
the  simple  reason  that  the  oil  is  vaporized  so  slowly  that 
the  inflammable  gas  produced  is  not  sufficient  to  support 
continuous  combustion. 

The  object  of  atomizing  the  oil,  or  dividing  it  into  a  fine 
mist  or  spray,  can  now  be  understood.  By  separating  the 
body  of  oil  into  a  great  number  of  fine  particles,  each  par^ 
ticle  will  have  its  surface  exposed  to  the  heat  and  will  be 
more  readily  vaporized  than  a  large  bulk  of  oil.  The  finer 
the  mist  or  spray,  the  more  easily  will  the  vaporizing  occur. 
This  can  be  shown  by  a  very  simple  example.  If  oil  is 
broken  up  into  a  series  of  drops  each  o.i  in.  in  diameter, 
the  ratio  of  the  surface  area  to  the  volume  of  each  drop 
is  sixty  to  one.  But  if  the  drops  are  o.oi  in.  in  diameter, 
the  ratio  of  area  to  volume  is  600  to  i.  That  is,  a  drop  of 
oil  o.oi  in.  in  diameter  will  expose  ten  times  as  much  sur- 
face per  unit  volume  as  a  drop  o.i  in.  in  diameter.  The 
finer  the  particles,  therefore,  the  greater  will  be  the 
amount  of  external  surface  per  unit  volume  exposed  to 
the  action  of  the  heat  and  the  more  rapidly  will  the  oil 
turn  to  vapor. 

When  the  oil  has  been  properly  vaporized,  it  must  be 


18  OIL  FUEL  FOR  STEAM  BOILERS 

thoroughly  mixed  with  air  in  the  correct  proportions  to 
produce  complete  combustion.  This  may  be  done  by 
allowing  the  air  to  enter  the  furnace  through  openings  in 
the  floor  or  the  ashpit,  somewhat  after  the  manner  in 
which  it  is  admitted  to  the  furnace  of  a  coal-burning 
boiler.  Again,  it  may  be  admitted  through  the  same 
openings  as  those  through  which  the  burners  are  intro- 
duced, in  which  case  the  air  sweeps  over  the  burners. 
But  it  is  more  than  probable  that  both  methods  will  be 
used  at  one  time,  so  that  part  of  the  necessary  air  will  be 
admitted  by  each. 

The  third  requirement  for  the  efficient  use  of  oil  fuel  is 
a  furnace  of  suitable  design  and  construction  in  which  the 
combustion  may  take  place.  The  common  furnace  used 
for  solid  fuel  will  not  ordinarily  answer  the  purpose  with- 
out alterations. 

The  coal-burning  furnace  can  be  fired  intermittently, 
for  there  is  always  a  bed  of  incandescent  fuel  on  the 
grates  so  that  when  the  fresh  coal  is  added  the  incandes- 
cent portion  will  fire  the  green  fuel.  But  the  injection 
of  the  liquid  fuel  is  continuous,  and  the  conversion  of  the 
freshly  admitted  oil  from  the  liquid  to  the  gaseous  state 
must  be  accomplished  by  a  part  of  the  heat  of  the  oil  that 
was  burned  just  before.  As  there  is  no  fuel  bed,  the  heat 
must  be  stored  in  the  lining  of  the  furnace.  In  other 
words,  the  furnace  is  lined  with  firebrick,  which  becomes 
highly  heated  and  acts  as  a  heat  reservoir  and  equalizer. 

The  chamber  in  which  the  combustion  of  the  liquid  fuel 
takes  place  should  not  be  bounded  by  cold  metal  surfaces. 
For  if  the  partly  burned  gases  strike  such  surfaces  they 
will  be  chilled,  combustion  will  be  checked,  and  there  will 


EFFICIENT  BURNING  OF  OIL  FUEL  19 

be  a  loss  of  heat  and  probably  the  formation  of  smoke. 
By  having  the  combustion  occur  in  a  firebrick  furnace, 
however,  the  chilling  is  prevented,  and  when  the  gases 
have  been  burned  completely  they  may  be  led  against  the 
boiler  tubes  and  surfaces  without  danger  of  producing 
smoke. 


CHAPTER  III 

METHODS  or  SPRAYING  OIL  FUEL 

The  atomizing  of  liquid  fuel,  or  the  breaking  up  of  the 
oil  into  a  spray  or  mist,  so  as  to  enable  the  air  to  mix 
thoroughly  with  it,  may  be  accomplished  in  a  number  of 
different  ways.  The  most  common  method  is  that  in 
which  a  current  of  steam  or  a  blast  of  air  is  directed  into 
or  across  the  flow  of  the  oil  so  as  to  divide  it  into  fine 
particles.  Another  way  is  to  subject  the  oil  to  a  high 
pressure  and  then  to  allow  it  to  escape  through  small 
orifices.  These  orifices  are  so  shaped  and  placed  that  the 
escaping  oil  is  expanded,  scattered  and  properly  atomized. 
A  third  method  involves  the  use  of  centrifugal  force.  A 
whirling  motion  is  given  to  the  oil,  and  the  centrifugal 
force  set  up  causes  the  oil  particles  to  fly  off  in  the  form 
of  spray. 

The  principles  involved  in  all  of  these  methods  are  used 
in  modern  liquid-fuel  burners,  but  centrifugal  force  alone 
is  not  relied  upon  to  produce  the  desired  atomization.  In 
the  lengthy  and  exhaustive  tests  made  by  the  Bureau  of 
Steam  Engineering  of  the  United  States  Navy  several 
attempts  were  made  to  use  an  atomizer  consisting  of  a 
steel  disk  that  was  rotated  at  a  high  speed  and  over 
which  the  oil  was  allowed  to  flow.  The  earlier  con- 
structions warped  under  the  effect  of  the  heat  or  were 
wrecked  by  the  centrifugal  force  developed,  but  by 

20 


METHODS  OF  SPRAYING  OIL  FUEL  21 

altering  the  construction  in  accordance  with  the  ex- 
perience gained  from  these  initial  experiments  a  centrifu- 
gal apparatus  was  eventually  produced. 

It  consisted  of  a  circular  disk  of  saw  steel  riveted  to  a 
hollow  pivot  that  was  held  solidly  in  vertical  bearings. 
Buckets  or  vanes  were  attached  in  a  circle  to  the  under 
side  of  the  disk,  and  a  jet  of  steam  from  a  single  nozzle 
was  directed  on  this  series  of  vanes,  thus  rotating  the  disk 
at  a  high  speed.  The  oil  to  be  sprayed  was  forced  up 
through  the  hollow  pivot  under  a  small  pressure  and  over- 
flowed on  to  the  disk  at  the  center.  Under  the  action  of 
the  centrifugal  force  set  up  by  the  very  rapid  rotation,  it 
was  flung  off  at  the  outer  edge,  and  when  ignited  by  a 
torch  it  burned  in  a  ring  of  flame  from  4  ft.  to  5  ft.  in 
diameter. 

In  spite  of  the  fact  that  a  mechanical  rotary  atomizer 
had  thus  been  developed,  this  type  has  not  been  adopted 
in  commercial  installations  using  oil  fuel.  The  reason  is 
that  the  spraying  force  is  derived  from  the  jet  of  steam, 
and  it  is  simpler  to  use  the  steam  directly  for  spraying, 
without  the  introduction  of  the  rotating  disk.  Also,  it  is 
probable,  from  the  results  of  the  experiments  referred  to, 
that  trouble  would  arise  through  warping  of  the  disk  and 
wearing  of  the  pivot.  It  is  true  that  the  flow  of  the  oil 
across  the  face  of  the  disk  has  a  tendency  to  cool  it  some- 
what and  thus  reduce  the  warping  effect,  but  the  fact 
remains  that  the  purely  centrifugal  sprayer  has  not  met 
with  favor. 

In  connection  with  pressure  spraying  from  an  orifice, 
however,  the  centrifugal  principle  has  been  used  success- 
fully. This  combination  may  be  illustrated  by  the  simple 


22 


OIL  FUEL  FOR  STEAM  BOILERS 


sketch  shown  in  Fig.  4.  At  the  end  of  the  pipe  a  that  con- 
veys the  oil,  the  oil  passage  b  is  tapered  down  to  the  open- 
ing c  through  which  the  oil  is  discharged.  The  series  of 
slanting  vanes  d  on  the  rod  e  deflect  the  oil  and  break  it  up 
into  a  number  of  currents,  each  of  which  has  a  whirling 

motion  as  it  enters  the  space  / 
around  the  end  g  of  the  rod. 
These  separate  currents  are 
intermingled  in  the  space  /, 
and  on  emerging  from  the  ori- 
fice c  they  spread  as  shown  by 
the  diverging  lines.  The  oil  is 
forced  into  the  pipe  a  under 
fairly  high  pressure,  and  thus 
the  atomizing  is  due  to  both 
the  twisting  motion  given  by 
the  vanes  and  the  expansion 
following  the  escape  at  high 
velocity  from  the  orifice. 

Though  the  principle  just  described  could  be  applied  in 
any  installation,  it  would  doubtless  be  most  advantageous 
in  the  case  of  a  plant  in  a  district  where  suitable  water  is 
scarce  or  hard  to  obtain.  For  the  steam  that  is  used  to 
atomize  the  oil  by  direct  action  goes  along  v.ith  the  prod- 
ucts of  combustion  and  escapes  at  the  top  of  the  chimney. 
It  is  thus  lost  absolutely,  so  far  as  the  chances  of  recover- 
ing it  are  concerned;  whereas  by  using  a  device  similar  to 
that  shown  in  Fig.  4  there  is  no  waste  of  steam.  It  is 
true  that  steam  would  be  required  to  run  the  pressure 
pumps,  but  it  could  afterward  be  led  to  some  form  of 
condenser  and  thus  recovered  for  boiler  feed-water. 


FIG.  4. — Atomizing  by 
pressure  and  centrifugal 
force  combined. 


METHODS  OF  SPRAYING  OIL  FUEL  23 

A  disadvantage  of  the  system  of  spraying  oil  by  pres- 
sure lies  in  the  fact  that  the  openings  through  which  the  oil 
is  forced  must  not  be  much  greater  than  1/16  in.  in 
diameter.  An  opening  of  this  small  size  can  very  easily 
become  clogged  by  a  bit  of  dirt  or  a  grain  of  sand;  there- 
fore, a  strainer  should  always  be  inserted  in  the  oil  system. 
The  holes  in  the  strainer,  of  course,  must  be  small  enough 
to  catch  and  retain  all  dirt  of  sufficient  size  to  clog  the 
burner.  Usually  they  are  made  about  half  the  size  of  the 
hole  or  holes  through  which  the  oil  is  sprayed. 

By  far  the  greater  number  of  oil-fuel  plants  use  steam 
or  air  as  the  atomizing  agent.  If  steam  is  used,  it  is 
obtained  from  the  boiler  being  fired  or  from  another  boiler 
in  the  plant,  and  if  air  is  used,  it  is  obtained  by  means  of  a 
positive  blower  or  an  air  compressor.  No  matter  which 
agent  is  used,  it  is  led  in  a  sheet  or  a  jet  against  the  oil  to 
be  atomized.  The  mixing  of  the  oil  and  the  steam  or  the 
air  may  take  place  inside  the  atomizing  device  or  outside 
it,  but  in  either  case  the  spraying  is  due  to  the  expansion 
that  occurs  when  the  steam  or  air  under  pressure  escapes 
from  the  orifice  and  mingles  with  the  oil. 

The  device  that  accomplishes  the  atomization  of  the  oil 
is  called  the  burner,  though  it  has  nothing  to  do  directly 
with  the  combustion.  There  are  two  main  classes  of 
burners,  namely,  outside  mixers  and  inside  mixers.  A 
common  form  of  outside-mixing  burner  is  shown  diagram- 
matically  in  Fig.  5.  The  oil  to  be  atomized  is  led  through 
the  passage  a  and  is  allowed  to  flow  out  and  down  at  the 
orifice  b.  The  steam  or  air  is  conducted  through  the 
passage  c  and  allowed  to  escape  through  the  narrow  ori- 
fice d  just  below  the  oil  orifice.  The  oil  that  oozes  or 


24 


OIL  FUEL  FOR  STEAM  BOILERS 


drools  out  is  thus  caught  by  the  rapidly  escaping  and 
expanding  steam  or  air  and  is  thoroughly  sprayed.  This 
type  is  ordinarily  termed  the  drooling  burner. 

Another  form  of  outside-mixing  burner  is  shown  in  Fig. 
6.  It  differs  from  the  other  only  in  that  the  oil  passage 
is  turned  downward  at  the  outlet  end,  and  the  steam  or 


FIGS.  5  and  6. — Principle  of  outside-mixing  burners. 

air  issuing  from  the  orifice  a  sweeps  directly  across  the 
face  of  the  oil  orifice  b.  This  type  is  called  the  atomizer 
burner. 

The  type  shown  in  Fig.  7  is  called  the  projector  burner 
and  also  belongs  to  the  outside-mixing  class.  In  this  case, 
however,  the  orifices  a  through  which  the  steam  or  air 


FIGS.  7  and  8.- 


-Principle  of  projector  burner  and  inside-mixing 
burner. 


escapes  are  at  some  distance  from  the  oil  orifices  b,  so  that 
the  steam  or  air  has  expanded  considerably  by  the  time  it 
meets  the  oil. 

One  form  of  inside-mixing  burner  is  shown  in  Fig.  8. 
The  oil  flows  into  the  chamber  a  surrounding  the  nozzle  b 
through  which  the  steam  or  air  is  led,  and  the  latter  meets 


METHODS  OF  SPRAYING  OIL  FUEL  25 

and  mingles  with  the  oil  in  the  chamber,  after  which  both 
are  discharged  at  c.  This  form  of  burner  is  termed  a 
chamber  burner. 

The  diagram  in  Fig.  9  illustrates  the  principle  of  the  in- 
jector burner.  The  steam  or  air  flows  from  the  orifice  a 
into  the  passage  b  containing  the  oil,  and  the  mixture  is 
carried  forward  with  increasing  velocity  toward  the  nar- 
rowest part  c  of  the  burner.  Beyond  this  throat  the 
mouth  is  flared,  and  the  rapid  expansion  atomizes  the  oil. 


\a    b 


FIG.  9. — Principle  of  injector  burner. 

The  various  types  of  burners  employed  in  steam  plants 
involve  the  use  of  one  or  more  of  the  foregoing  principles. 
Air  is  used  only  in  special  instances  as  the  atomizing  agent, 
steam  being  the  most  common.  So  far  as  economy  is  con- 
cerned, there  is  little  to  choose  between  the  two,  for  the 
reason  that  the  amount  of  steam  required  for  direct  atom- 
izing is  about  the  same  as  that  required  to  run  an  air 
compressor  to  furnish  a  sufficient  supply  'of  air  at  the 
necessary  pressure.  On  the  other  hand,  the  addition  of 
a  compressor  means  increased  cost  for  installation  over 
that  for  a  plant  using  steam  directly;  also,  the  amount  of 
piping  and  apparatus  is  increased  by  the  use  of  a  compres- 
sor, with  the  natural  result  that  accidents  are  more  likely 
to  happen  and  so  cause  partial  or  complete  shut-downs. 

The  amount  of  steam  used  to  atomize  i  Ib.  of  oil, 
whether  directly  or  indirectly,  may  be  taken  as  about  0.5 


26  OIL  FUEL  FOR  STEAM  BOILERS 

lb.  for  average  cases.  There  are  plants  in  which  only 
about  0.3  lb.  of  steam  per  pound  of  oil  is  used  for  atomiza- 
tion, and  in  the  tests  made  by  the  Bureau  of  Steam  Engi- 
neering some  burners  used  as  low  as  0.15  lb.  of  steam  per 
pound  of  oil.  This  last  was  an  exceptionally  good  per- 
formance and  was  unusual.  The  average  plant  may  con- 
sider that  its  economy  is  fair  if  its  steam  consumption  for 
atomization  only  amounts  to  from  0.3  lb.  to  0.5  lb.  per  lb. 
of  oil. 

In  addition  to  the  steam  required  for  atomizing  the  oil, 
there  is  the  steam  required  for  running  the  pumps  by 
which  the  oil  is  supplied  under  pressure  and  the  steam 
used  in  some  cases  for  heating  the  oil.  The  amount  of 
steam  used  for  atomization  is  roughly  2  per  cent,  of  the 
total  amount  generated  by  the  boiler;  that  is,  out  of  every 
100  lb.  of  steam  formed,  2  lb.  are  taken  to  spray  the  oil. 
The  oil-pressure  pumps  and  the  oil  heater  require  about 
2  per  cent,  more,  so  that  the  total  steam  consumption  of 
the  oil  system  is  in  the  neighborhood  of  4  per  cent,  of  the 
steam  generated. 


CHAPTER  IV 

BURNERS  FOR  OIL  FUEL 

The  purpose  of  the  burner  is  to  spray  the  oil  fuel  into  the 
furnace;  consequently  the  first  requisite  of  a  good  burner 
is  that  it  shall  atomize  the  fuel  satisfactorily.  As  oils  are 
of  different  densities  and  viscosities,  and  as  different  rates 
of  feed  must  be  used  to  accommodate  the  rate  of  com- 
bustion to  the  load  on  the  boiler,  it  follows  that  the  burner 
must  be  fitted  with  suitable  valves  in  order  that  its  action 
may  be  regulated  closely.  This  regulation  applies  not 
only  to  the  oil  but  to  the  atomizing  medium  as  well. 

A  second  important  feature  of  a  good  burner  is  accessi- 
bility for  cleaning  and  repair.  It  is  almost  impossible, 
even  after  taking  the  precaution  of  cleaning  and  strain- 
ing, to  prevent  dirt  from  being  carried  along  with  the  oil. 
As  a  result,  clogging  of  the  oil  orifices  may  occur,  and  it 
then  becomes  necessary  to  clean  the  burner.  To  do  this 
easily  and  quickly,  the  burner  must  be  designed  so  that  it 
may  be  taken  apart  readily  and  without  undue  labor. 
In  some  types  of  burners  the  oil  and  steam  currents  cause 
erosion,  and  in  such  forms  it  is  necessary  to  make  provi- 
sion for  removing  and  renewing  the  worn  parts  without 
loss  of  time. 

A  form  of  Gem  burner  designed  particularly  for  use  in 
small  furnaces  is  shown  in  Fig.  10.  Its  body  a  is  of  cast 
iron  and  contains  two  inlets  b  and  c,  the  former  for  the  oil 

27 


28 


OIL  FUEL  FOR  STEAM  BOILERS 


and  the  latter  for  the  steam  that  is  used  as  the  spraying 
agent.  The  oil  flows  along  the  central  pipe  d  and  escapes 
at  the  tip  of  the  burner.  The  steam  passes  along  the  pipe 
e  surrounding  the  oil  pipe  and  is  given  a  whirling  motion 
by  the  vanes  of  the  whorl  /  near  the  tip.  It  then  escapes 
past  the  conical  end  of  the  oil  pipe,  through  an  annular 
opening  g,  sweeping  the  oil  into  the  furnace. 


FIG.  10. — Regular  Gem  oil  burner. 

As  the  oil  pipe  a  is  surrounded  by  live  steam  throughout 
its  entire  length,  the  oil  becomes  well  heated  in  flowing 
through  the  burner,  and  the  effect  of  this  heating  is  to 
make  it  more  fluid  and  easy  to  atomize.  The  regulation 
of  the  flow  of  oil  and  steam  is  accomplished  by  valves  in 
the  pipes  attached  at  b  and  c  respectively,  since  there  are 
no  moving  parts  in  the  burner  itself.  Should  the  oil  pipe 
become  clogged  with  dirt,  the  cap  at  the  back  may  be 
unscrewed  and  a  rod  may  be  inserted  to  remove  the 
obstruction. 

An  improved  form  of  this  burner  is  shown  in  Fig.  n. 
It  differs  from  the  form  shown  in  Fig.  10  mainly  in  that 


BURNERS  FOR  OIL  FUEL 


29 


it  has  a  needle  valve  included  in  the  burner  to  enable  the 
oil  flow  to  be  regulated  more  closely.  The  stem  a,  Fig.  1 1, 
of  the  needle  valve  is  threaded  near  its  inner  end  and 
passes  through  a  stuffing-box  b  at  its  outer  end;  thus  any 


FIG.  ii. — Improved  Gem  oil  burner. 

expansion  of  the  stem  due  to  increase  of  temperature  does 
not  alter  the  adjustment  of  the  valve,  as  it  would  do  if  the 
stem  were  threaded  at  the  stuffing-box  end.  The  oil  sur- 
rounds the  stem  inside  the  pipe  c  and  flows  to  the  nozzle 
through  grooves  cut  in  the  side  of  the  stem.  The  atomi- 


FIG.  12. — Parson  oil  burner. 

zation  is  effected  in  the  same  way  as  in  the  simpler  type. 
Each  of  these  burners  may  easily  be  unscrewed  and  taken 
apart  for  cleaning. 

The  Parson  burner  illustrated  in  Fig.  12  is  similar  in 


30 


OIL  FUEL  FOR  STEAM  BOILERS 


principle  to  that  shown  in  Fig.  n.  The  tip  a  of  the 
Parson  burner  has  a  passage  b  for  the  steam,  which  is 
admitted  through  the  connection  c.  The  oil  enters  at  d' 
and  flows  into  the  chamber  e,  from  which  it  is  allowed  to 
pass  into  the  nozzle  /  past  the  regulating  valve  g.  This 
valve  has  a  very  slight  taper,  and  consequently  the  flow 


f"l 


9       9 


FIG.  13. — Booth  oil  burner  with  pipe  connections. 

of  oil  can  be  adjusted  with  great  precision.  The  nozzle 
projects  through  the  center  of  the  steam  passage  in  the 
tip,  and  the  oil  is  thus  heated  on  its  way  to  the  furnace. 
The  valve  stem  h  is  furnished  with  a  stuffing-box  i  to 
prevent  the  leakage  of  oil. 

The  Booth  burner,  shown  in  Fig.  13,  is  one  that  has  been 
used  extensively  in  stationary-boiler  practice.     The  body 


BURNERS  FOR  OIL  FUEL  31 

of  the  burner  consists  of  a  box-shaped  casting  a  that  is  set 
horizontally.  It  contains  two  passages  b  and  c,  oil  being 
admitted  to  the  former  through  the  pipe  d  and  steam  to 
the  latter  through  the  pipe  e.  The  oil  flows  outward 
through  the  wide,  shallow  slot  /  at  the  tip  of  the  burner 
and  drools  downward  across  the  end.  An  adjustable  steel 
plate  g  is  bolted  across  the  steam  orifice.  This  plate  has 
a  long  notch  cut  in  the  top  edge,  forming  the  outlet  h  for 
the  steam,  and  on  the  inside  it  is  beveled  or  chamfered  so 
as  to  direct  the  steam  upward  toward  the  orifice.  The 
escaping  steam  sweeps  along  the  under  side  of  the  burner 
tip  and  in  expanding  sprays  the  oil  that  runs  down  from 
the  upper  slot.  The  bolts  that  hold  the  plate  g  in  place 
pass  through  long  vertical  slots  in  the  plate,  and  this  con- 
struction allows  the  plate  to  be  moved  up  or  down  to  give 
the  desired  depth  of  slot  h.  This  adjustment,  of  course, 
is  made  when  the  burner  is  disconnected  and  not  in  use. 
The  arrangement  of  the  piping  to  the  Booth  burner  is 
simple.  The  supply  of  steam  is  brought  to  the  burner 
through  the  pipe  £,  the  flow  being  regulated  by  the  valve  i. 
In  the  same  way  a  valve  j  in  the  oil  line  d  is  used  to  con- 
trol the  rate  of  flow  of  the  oil.  Between  the  oil  pipe  and 
the  steam  pipe  is  inserted  a  short  connection  fitted  with  a 
valve  k.  This  serves  as  a  by-pass  to  admit  steam  to  the 
oil  passage  when  it  becomes  necessary  to  clean  out  the 
passage.  The  oil  valve  j  and  the  steam  valve  i  are  first 
closed  and  then  the  by-pass  valve  k  is  opened.  The 
steam  rushes  through  the  oil  passage,  and  its  heat  and  its 
cutting  action  together  scour  the  passage  clean.  The 
steam  passage  may  be  cleaned  by  removing  the  plate  g 
completely  and  allowing  steam  to  blow  through  at  full 


32 


OIL  FUEL  FOR  STEAM  BOILERS 


pressure.  The  passages  in  the  burner  are  straight  and 
fairly  large,  and  there  is  little  danger  of  their  becoming 
clogged  frequently. 

A  form  of  externally  atomizing  burner  known  as  the 
Best  burner  is  shown  in  Fig.  14.  The  tip  by  which  the 
atomizing  is  accomplished  is  supported  by  two  pipes  a 
and  b  that  convey  the  steam  and  the  oil,  and  these  pipes 
are  made  of  such  length  that  they  will  extend  through  the 


a 


FIG.  14. — Best  oil  burner. 


boiler  front  and  bring  the  burner  just  within  the  front  of 
the  furnace.  The  tip  is  of  cast  iron  and  contains  a  steam 
passage  c  and  an  oil  passage  d  connecting  with  the  oil  pipe 
b.  The  oil  passage  is  curved  upward,  so  that  the  escaping 
steam  sweeps  across  the  face  of  the  orifice  e  at  right  angles 
to  the  direction  of  flow  of  the  oil,  thus  insuring  excellent 
atomization.  Moreover,  it  is  stated  that  this  arrange- 
ment of  the  two  orifices  causes  the  steam  to  have  a  sort  of 
ejector  action  on  the  oil,  with  the  result  that  the  oil  is 


BURNERS  FOR  OIL  FUEL  33 

drawn  toward  the  orifice  e  and  only  a  low  pressure  is 
necessary  in  the  oil  system. 

The  steam  orifice  /  is  a  long,  shallow  slot  in  the  under 
face  of  a  hinged  lip  g  that  during  the  normal  working  of 
the  burner  is  held  down  firmly  against  the  body  of  the  tip. 
A  fork  h  is  pinned  to  the  lip  and  has  fastened  to  it  a  rod  i 
that  is  threaded  at  its  outer  end  and  fitted  with  two  ad- 
justing nuts  j  and  k  on  opposite  sides  of  the  bracket  /. 
When  the  steam  passage  becomes  clogged  or  choked, 
these  nuts  are  turned  so  as  to  force  the  rod  i  inward  and 
swing  the  lip  upward.  Full  steam  pressure  is  then  turned 
on  to  blow  out  the  obstruction,  after  which  the  lip  is 
drawn  down  on  its  seat.  This  may  be  done  from  the 
front  of  the  boiler  without  disturbing  the  setting  of  the 
burner.  The  flow  of  oil  is  regulated  by  a  cock  m  and  the 
steam  supply  by  a  valve  n  in  the  steam  pipe.  A  by-pass 
valve  o  is  inserted  between  the  steam  and  oil  pipes,  to 
enable  the  oil  side  of  the  burner  to  be  cleaned  out  readily, 
as  explained  before. 

The  construction  of  the  Best  burner  is  such  that  there 
is  little  or  no  wear,  and  the  absence  of  needle  adjusting 
valves  and  constricted  passages  reduces  the  likelihood  of 
clogging.  If  desired,  this  burner  may  be  operated  with 
tar  as  fuel,  and  it  is  equally  serviceable  with  heavy  oils. 
The  flame  produced  is  fan-shaped  and  spreads  to  about 
the  width  of  the  boiler  furnace. 

The  Hammel  burner,  shown  in  perspective  and  in  sec- 
tion in  Fig.  15,  belongs  to  the  inside-mixing  type.  It  con- 
sists of  three  main  parts  a,  b,  and  c,  held  together  by  bolts 
d  and  e.  The  lower  part  a  contains  the  passage/  through 
which  steam  is  admitted  to  the  burner,  and  the  upper 


34 


OIL  FUEL  FOR  STEAM  BOILERS 


section  b  has  the  oil  connection  g  from  which  a  duct  h 
leads  downward  to  a  mixing  chamber  i  formed  by  a  recess 
in  the  under  side  of  the  section  c.  The  steam  flows  up 
from  the  passage  /  into  the  chamber  j,  from  which  three 
slanting  ducts  k,  I  and  m  lead  to  the  mixing  chamber. 
These  ducts  are  inclined  in  different  directions,  and  their 
lower  ends  are  grouped  about  the  end  of  the  oil  duct  h  in 


FIG.  15. — Hammel  oil  burner. 

such  a  way  that  the  escaping  steam  will  mingle  thoroughly 
with  the  oil  in  the  mixing  chamber.  From  the  mixing 
chamber  a  flaring  opening  n  extends  outward  to  the  tip 
of  the  burner,  and  as  the  steam  flows  at  high  velocity 
and  escapes  from  the  wide  orifice  o,  it  spreads  the  oil  and 
causes  the  burner  to  produce  a  fan-shaped  flame. 

Experience  with  steam  turbines  has  shown  that  steam 
traveling  at  high  speed  has  an  erosive  effect  on  pipe 


BURNERS  FOR  OIL  FUEL 


35 


fittings,  valves,  vanes  and  other  parts  that  deflect  its 
motion.  This  cutting  action  is  present  likewise  in  oil 
burners  that  use  steam  as  the  atomizing  agent,  and  in  the 
Hammel  burner  the  erosion  is  greatest  in  the  divergent 
mouth  n.  The  wear  is  due  to  the  cutting  action  of  wet 
steam  and  to  the  presence  of  particles  of  dirt  and  grit  in 
the  oil.  As  a  consequence,  the  upper  and  lower  faces  of 
the  opening  n  are  lined  with  steel  plates  p  and  q  that  take 


FIG.  1 6. — Piping  for  Hammel  burner. 

all  the  wear  and  that  may  be  renewed  at  small  cost  when 
they  become  greatly  eroded.  To  insert  new  plates,  the 
bolts  d  are  unscrewed  and  the  section  c  is  removed,  thus 
uncovering  the  plates.  The  set  screw  r  serves  to  hold 
the  upper  plate  p  firmly  in  place  when  the  burner  is  put 
together. 

The  Hammel  burner  is  attached  to  the  ends  of  tfre 
steam  and  oil  pipes,  as  shown  in  Fig.  16,  and  these  pipes 
are  made  of  suitable  lengths  to  allow  the  burner  to  project 
into  the  furnace  through  the  front  of  the  boiler  setting. 


36 


OIL  FUEL  FOR  STEAM  BOILERS 


The  valve  a  regulates  the  flow  of  oil  and  the  valve  b  the 
flow  of  steam.  The  valve  c  acts  as  a  by-pass  for  use  in 
cleaning  out  the  burner  in  case  it  becomes  choked  with 
grit  or  carbonized  oil. 

A  perspective  view  of  the  Kirkwood  burner  is  given  in 
Fig.  17,  and  in  Fig.  18  is  a  longitudinal  section  of  the 
burner,  together  with  the  arrangement  of  the  piping. 


FIG.  17. — Regular  Kirkwood  oil  burner. 

The  same  reference  letter  is  used  to  designate  correspond- 
ing parts  that  appear  in  both  views.  The  main  part  of 
the  burner  is  a  hollow  casting  a  into  which  the  steam 
supply  pipe  b  is  screwed.  A  plug  c  is  inserted  at  one  end 
and  at  the  other  is  a  stuffing-box  d  through  which  the 
pipe  e  extends  into  the  chamber  /.  At  its  outer  end  the 
pipe  e  is  threaded  and  passes  through  a  threaded  collar  g 
that  may  be  rotated  in  the  bracket  h  by  mecins  of  the 
handle  i.  At  the  inner  end  the  pipe  is  closed  by  a  plug  j 
containing  an  orifice  k  that  may  be  closed  by  screwing 
the  long  stem  /  inward  until  it  seats  against  the  plug.  A 
handle  m  is  fastened  to  the  outer  end  of  the  stem  and 
carries  a  pointer  n  that  moves  over  the  dial  on  the  end  of 
the  flange  o  on  the  elbow  p.  The  supply  of  oil  is  admitted 
from  the  pipe  q  through  the  elbow  p  to  the  pipe  e,  and  it 


BURNERS  FOR  OIL  FUEL 


37 


escapes  past  the  regulating  stem  /  through  the  orifice  k, 
where  it  is  picked  up  by  the  steam  flowing  into  the  cham- 
ber /  and  carried  through  the  opening  r  into  the  furnace. 
The  handle  i  carries  a  pointer  s  that  moves  over  a  dial 
on  the  face  of  the  bracket  h.  Movement  of  the  handle  i 


FIG.  1 8, — Piping  for  Kirkwood  burner. 

governs  the  position  of  the  plug  j  with  respect  to  the  plug 
c  and  so  determines  the  amount  of  steam  used  for  atomiz- 
ing the  oil.  The  position  of  the  stem  /  is  regulated  by  the 
handle  m,  thus  governing  the  rate  of  flow  of  oil.  The  two 
dials  enable  the  fireman  or  the  boiler  attendant  to  adjust 
the  flow  of  steam  and  oil  very  accurately  after  he  has 


38 


OIL  FUEL  FOR  STEAM  BOILERS 


once  determined  the  relative  proportions  that  give  the 
best  results.  By  having  the  regulating  valves  very  close 
to  the  point  where  the  steam  and  oil  mingle,  as  in  this 
burner,  the  full  pressure  of  each  is  maintained  up  to  the 
moment  of  its  escape.  The  valve  /  is  a  by-pass  valve 
through  which  steam  may  be  admitted  to  the  oil  pipe  to 
clean  it.  A  slip  joint  is  sometimes  inserted  in  the  hori- 
zontal section  u  of  the  by-pass  pipe  to  allow  easy  sliding 
when  the  oil  pipe  e  is  moved  in  or  out  by  the  handle  i. 


FIG.  19. — Koerting  centrifugal  spray  nozzle. 

The  setting  or  adjustment  of  the  oil-regulating  stem  is 
not  affected  by  the  movement  of  the  pipe  e  because  the 
latter  is  fixed  rigidly  to  the  elbow  p  through  which  the 
stem  passes,  so  that  any  movement  of  the  pipe  carries  the 
stem  along  without  changing  its  distance  from  the  plug  k. 
The  construction  of  the  Koerting  centrifugal  spray 
nozzle  is  shown  by  the  section  in  Fig.  19.  The  burner 
consists  of  a  casting  a  that  is  inserted  in  a  suitable  opening 
in  the  boiler  front  and  that  in  turn  has  an  opening  b 
through  which  the  tips  c  of  the  spray  nozzles  may  project. 
There  are  two  of  these  nozzles  held  in  the  casting  d  that 


BURNERS  FOR  OIL  FUEL  39 

contains  the  oil  passages  and  strainers.  The  tip  c  has  at 
its  end  a  small  orifice  that  is  expanded  inward  to  form  a 
chamber  to  contain  the  screw  e,  which  is  carried  by  a  stem 
/  that  fits  in  the  plug  g,  and  is  held  in  position  by  the 
pressure  of  the  spring  h.  The  oil  enters  through  the  pipe 
i  and  passes  through  the  strainer  j  on  its  way  to  the  spray 
nozzle,  thus  being  cleaned.  The  cage  k  that  carries  the 
strainer  is  screwed  into  the  casting  d  and  may  be  taken 
out  for  cleaning  by  first  removing  the  cap  /.  The  oil  is 
sprayed  by  the  whirling  set  up  by  the  screw  in  the  tip  of 
the  nozzle,  in  combination  with  the  pressure  maintained 
in  the  oil  system.  The  air  required  for  combustion  is 
admitted  through  registers  around  the  outside  of  the 
casting  a.  The  stems/  are  held  by  springs  so  that,  when 
heated,  they  may  expand  freely.  If  they  were  held  down 
by  the  direct  pressure  of  the  plugs  g,  any  expansion  due 
to  heating  would  cause  them  to  buckle.  The  screws  e 
may  be  removed  for  cleaning  by  taking  out  the  plugs  g. 
In  all  of  the  types  of  burners  heretofore  described  the 
relative  proportions  of  the  atomizing  agent  and  the  oil  are 
under  the  control  of  the  operator.  The  Kirkwood  burner 
shown  in  section  in  Fig.  20  belongs  to  that  class  in  which 
the  relative  sizes  of  the  openings  for  oil  and  steam  or  air 
are  fixed  during  the  construction  or  assembling  of  the 
burner.  The  oil  and  the  steam  enter  through  the  pipes  a 
and  b,  respectively,  which  are  connected  to  opposite  sides 
of  the  body  casting  c.  The  regulation  of  the  flow  of  oil 
and  steam  is  accomplished  by  turning  the  single  handle  d, 
which  is  threaded  on  the  boss  e  and  carries  the  stem  /. 
This  stem  is  hollow  and  is  drilled  with  lateral  holes  g  that 
connect  with  the  oil  supply.  At  its  inner  end  it  is  tapered 


40 


OIL  FUEL  FOR  STEAM  BOILERS 


to  fit  a  seat  in  the  plug  h.  A  tapered  stem  i  is  fixed  cen- 
trally in  this  plug  and  projects  into  the  hollow  stem  /. 
When  the  handle  d  is  turned  to  the  right  as  far  as  it  will 
go,  the  stem  i  closes  the  duct  j  and  at  the  same  time  the 
tapered  end  of  the  stem  /  comes  against  its  seat  in  the 
plug  h  and  shuts  off  the  flow  of  steam  to  the  tip  k  of  the 


FIG.  20. — Kirkwood  burner  with  fixed  steam-to-oil  ratio. 

burner.  In  this  way  the  burner  is  shut  down.  By 
turning  the  handle  in  the  opposite  direction,  both  steam 
and  oil  are  admitted  to  the  mixing  chamber  /,  the  relative 
proportions  being  governed  by  the  taper  of  the  stems  / 
and  i.  The  position  of  the  stem  is  fixed  by  the  manu- 
facturer and  cannot  easily  be  changed  by  the  operator. 
This  removes  the  danger  of  having  an  unskilled  operator 


BURNERS  FOR  OIL  FUEL 


41 


affect  the  efficiency  of  the  burner  by  changing  the  relative 
amounts  of  oil  and  steam. 

The  outside-mixing  burner  in  Fig.  21  illustrates  a  type 
that  is  made  in  a  number  of  forms  differing  only  slightly 
in  detail.  The  steam  pipe  a  and  the  oil  pipe  b  are  made 


FIG.  21. — Slot  oil  burner  with  renewable  disk. 

of  such  length  as  to  bring  the  tip  of  the  burner  to  the 
proper  point  in  the  furnace.  The  burner  consists  of  two 
cup-shaped  castings  c  andd  separated  by  a  narrow  disk  e. 
The  three  pieces  are  of  the  same  diameter  and  are  held 
together  firmly  by  the  central  bolt  /.  As  shown  in  the  sepa- 


42  OIL  FUEL  FOR  STEAM  BOILERS 

rate  views,  the  disk  ghas  its  rim  cut  away  on  both  sides  for 
about  one-third  of  its  circumference.  Thus,  when  it  is 
bolted  between  the  castings  c  and  d,  two  slots  g  and  h  are 
formed,  extending  about  one-third  of  the  way  around  the 
burner.  The  oil  flows  through  the  upper  casting  c  and 
drools  over  the  edge  of  the  disk  e  from  the  slot  g.  The 
steam  flows  through  the  lower  casting  d  and  escapes 
through  the  slot  h,  meeting  the  oil  and  spraying  it  so  as  to 
produce  a  wide  fan-shaped  flame.  The  greater  part  of 


FIG.  22. — Inside-mixing  slot  oil  burner. 

the  wear  due  to  erosion  comes  on  the  disk  e,  which  can  be 
renewed  when  badly  worn.  The  arrangement  of  the  regu- 
lating valves  for  oil  and  steam  and  of  the  by-pass  for 
cleaning  is  similar  to  that  already  described. 

Another  form  of  inside-mixing  slot  burner  differing 
considerably  from  the  Hammel  burner  is  shown  in  section 
in  Fig.  22.  The  steam  enters  at  a  and  flows  out  through 
the  holes  in  the  conical  tip  of  the  section  b  into  the  narrow 
passage  c.  The  oil  enters  at  d  and  flows  around  the  sec- 
tion b,  being  heated  in  so  d$ing.  Under  its  own  pressure, 


BURNERS  FOR  OIL  FUEL  43 

and  aided  by  the  suction  produced  by  the  escaping  steam, 
it  flows  past  the  conical  tip,  where  it  is  caught  by  the 
steam,  broken  up,  and  carried  along  the  pipe  c.  Further 
mixing  of  the  steam  and  oil  takes  place  in  the  chamber 
and  the  spray  escapes  through  the  slot  e  into  the  furnace. 
The  spread  of  the  flame  may  be  changed  by  using  slots  of 
different  proportions. 


CHAPTER  V 
CLEANING  or  OIL  FUEL 

The  greater  number  of  burners  for  oil  fuel  are  con- 
structed with  small  orifices  through  which  the  oil  is 
sprayed.  It  therefore  becomes  necessary  to  take  proper 
precautions  to  prevent  the  burners  from  becoming  clogged 
by  particles  of  sand  or  other  foreign  matter.  The  dirt 
found  in  the  oil  may  be  in  the  crude  oil  as  it  comes  from 
the  well,  or  it  may  find  its  way  in  during  the  subsequent 
transportation  and  handling  of  the  oil.  Oil  wells  are 
driven  through  strata  of  various  earthy  materials  to  pierce 
the  oil-bearing  sands,  and  as  a  consequence  the  crude  oil 
issuing  from  a  well  contains  more  or  less  sand.  If  the 
crude  oil  is  used  directly  as  a  boiler  fuel,  it  must  be 
strained;  otherwise  the  particles  of  sand  will  clog  the 
burners  and  render  them  erratic  in  their  operation. »  The 
heavier  and  more  viscous  the  oil,  the  more  easily  will  it 
hold  and  carry  with  it  particles  of  sand  and  dirt. 

A  common  method  of  separating  dirt  held  in  suspen- 
sion in  liquids  of  smaller  specific  gravity  is  that  of  sedi- 
mentation or  settling.  Thus,  if  oil  fuel  containing  dirt  is 
run  into  storage  reservoirs  or  settling  tanks  and  there 
allowed  to  remain  undisturbed  for  some  time,  much  of  the 
heavier  sediment  will  fall  to  the  bottom  by  reason  of  its 
own  greater  density.  The  cleaned  oil  may  then  be  drawn 
off  at  the  top.  However,  this  method  involves  storage  of 

44 


CLEANING  OF  OIL  FUEL  45 

the  oil  for  a  time,  with  the  consequent  expense  of  tanks 
and  pumping  machinery;  moreover,  if  the  oil  is  very  heavy 
and  viscous,  it  is  by  no  means  certain  that  the  settling 
method  will  result  in  thorough  cleaning.  It  is  therefore 
a  wise  precaution  to  use  strainers  in  the  piping  system 
that  conveys  the  oil  to  the  burners. 

Even  the  heat  treatment  or  partial  distillation  that  re- 
sults in  the  formation  of  fuel  oil  cannot  be  relied  on  to  pro- 
duce a  clean  oil ;  so,  where  fuel  oil  is  used,  strainers  should 
be  installed.  They  not  only  prevent  clogging,  but  they 
also  lessen  the  wear  on  the  burner  tips  due  to  the  erosive 
effect  of  grit. 

The  material  of  which  the  strainer  is  made  may  be  wire 
netting,  gauze  or  perforated  metal.  In  any  case,  the 
meshes  or  openings  should  be  only  about  half  as  wide  as 
the  smallest  passage  or  orifice  in  the  burner.  Brass  wire 
gauze  is  the  material  commonly  used,  although  good 
strong  mosquito  netting  may  be  bent  into  shape  to  form 
a  strainer.  On  account  of  the  comparatively  large  open- 
ings in  mosquito  netting,  it  should  be  used  only  in  connec- 
tion with  burners  that  have  no  minute  orifices,  as,  for 
example,  the  Best  burner. 

The  simplest  form  of  strainer,  shown  in  Fig.  23,  con- 
sists of  a  circular  piece  of  wire  gauze  a  held  between  a 
pair  of  pipe  flanges  b  and  c\  but  the  simplicity  and  cheap- 
ness of  this  form  are  its  only  commendable  features.  The 
oil  flowing  from  the  pipe  d  to  the  pipe  e  on  its  way  to  the 
burners  will  deposit  the  sand  and  dirt  on  the  gauze,  and 
sooner  or  later  the  latter  will  become  choked,  because  it 
has  so  small  an  area.  In  this  condition  it  will  seriously 
obstruct  the  flow  of  oil;  therefore,  a  strainer  of  this  kind 


46 


OIL  FUEL  FOR  STEAM  BOILERS 


would  have  to  be  cleaned  frequently.  Each  cleaning 
would  necessitate  opening  up  the  joint  at  the  flanges,  so 
that  the  gauze  could  be  taken  out,  and  before  this  could 
be  done  it  would  be  necessary  to  shut  off  the  flow  of  oil. 
This  type  of  strainer,  therefore,  is  to  be  avoided  in  the 
simple  form  shown. 

The  arrangement  of  piping  shown  in  Fig.  24  does  away 
with  the  objectionable  feature  of  breaking  the  joint  to 


FUGS.  23  and  24. — Simple  oil  strainer  and  piping  for  strainer. 

clean  the  strainer.  The  oil  from  the  pump  flows  through 
the  pipe  a  and  the  valve  b  and  passes  upward  through  the 
wire  gauze  held  between  the  flanges  at  c,  continuing  on  its 
way  to  the  burners  through  the  valve  d  and  the  pipe  e. 
The  steam  line  /  to  the  burners  has  a  branch  g  that  is 
joined  by  the  T  h  to  the  oil  line  and  is  fitted  with  a  valve 
i.  Below  the  strainer  the  oil  pipe  is  extended  and  fitted 
with  a  valve/.  When  the  burners  are  working,  the  valves 
i  and/  are  closed  and  the  valves  b  and  d  are  open.  When 


CLEANING  OF  OIL  FUEL  47 

the  strainer  becomes  clogged  and  requires  cleaning,  the 
valves  b  and  d  are  closed  and  a  bucket  is  placed  under  the 
valve  jj  which  is  then  opened.  Finally,  .the  valve  i  is 
slowly  opened,  admitting  live  steam  above  the  strainer, 
and  this  steam,  rushing  downward  through  the  gauze,  will 
clean  it  and  blow  out  all  the  dirt  collected  beneath  it. 
The  valves  are  then  set  again  for  normal  working.  The 
valve  2' must  be  tight  or  condensed  steam  will  leak  into  the 
oil  and  cause  the  burners  to  sputter.  The  nipple  k  should 
be  fairly  long,  to  form  a  trap  for  water  and  dirt.  A 
pressure  gage,  shown  at  /,  may  be  attached  to  the 
oil  pipe  on  the  pump  side  of  the  strainer.  An  abnormal 
rise  of  pressure  shown  on  it  will  indicate  that  the  strainer 
is  clogged  and  in  need  of  cleaning. 

The  requirements  of  a  good  oil  strainer  are  that  it  shall 
stop  and  hold  the  solid  foreign  matter  entrained  with  the 
oil,  that  it  shall  have  ample  straining  surface,  so  that 
cleaning  may  not  be  required  too  frequently,  and  that 
it  shall  be  constructed  and  installed  so  that  the  cleaning 
may  be  quickly  and  easily  done. 

The  strainer  shown  in  Fig.  25  is  made  of  wire  gauze 
bent  into  the  form  of  a  conical  frustum,  with  the  large  end 
a  open  and  the  small  end  b  closed.  This  form  is  inserted 
in  the  open  end  of  the  suction  pipe  c  leading  to  the  oil 
pump  and  provides  a  large  area  through  which  the  oil 
may  pass  on  its  way  to  the  pump.  An  advantage  of 
having  the  strainer  at  this  point  is  that  it  removes  much  of 
the  grit  that  would  otherwise  cause  wear  of  the  pump 
barrel  and  plunger.  The  large  end  a  is  made  slightly 
larger  than  the  diameter  of  the  suction  pipe.  The 
strainer  is  simply  pressed  into  place  in  the  pipe  and  is 


48 


OIL  FUEL  FOR  STEAM  BOILERS 


held  there  by  friction  and  by  the  suction  effect  of  the 
pump.  A  bail  or  loop  d  is  fastened  to  the  large  end 
so  that  the  strainer  may  easily  be  withdrawn  when  it 
must  be  cleaned.  The  tapering  form  allows  ample  space 
around  the  strainer,  as  at  e,  for  the  oil  after  it  has  passed 
through  the  gauze. 


FIGS.  25   and  26. — Suction-pipe  strainer  and  T-fitting  used  for 
strainer. 

A  T-fitting  may  be  used  to  form  a  simple  and  inexpen- 
sive strainer,  as  shown  in  Fig.  26.  The  fitting  a  is  in- 
serted at  a  right-angled  turn  in  the  oil  piping,  and  the  oil, 
entering  through  the  pipe  ft,  passes  through  the  strainer 
c  and  flows  away  through  the  pipe  d.  The  strainer  is 
cylindrical  in  shape  and  hangs  in  the  pipe  d,  being 


CLEANING  OF  OIL  FUEL 


49 


supported  by  a  ring  e  that  rests  on  the  upper  end  of  the 
pipe.  When  the  strainer  requires  cleaning,  the  plug/  is 
removed  and  the  strainer  is  lifted  out  by  the  bail  g. 

The  type  of  strainer  shown  in  Fig.  27  consists  of  a 
special  casting  a  that  is  installed  in  the  oil  line  and  that 
contains  the  perforated  metal  cylinder  b  by  which  the 
actual  straining  is  done.  The  oil  enters  at  c  and 
flows  out  at  d.  The  cylinder  b  may  easily  be  removed 


FIGS.  27  and  28. — Perforated  metal  strainer  and  basket  strainer 
for  quick  cleaning. 

after  the  plug  e  is  unscrewed;  but,  as  in  the  case  of  the 
strainers  previously  shown,  the  flow  of  oil  must  be  shut 
off  during  the  cleaning  operation.  In  order  to  reduce  the 
period  of  stoppage  to  a  minimum,  it  is  advisable  to  have 
more  than  one  perforated  cylinder,  so  that  a  clean  one 
can  be  inserted  as  soon  as  the  dirty  one  is  removed. 
Any  dirt  that  passes  through  the  strainer  and  settles  in 
the  bottom  of  the  chamber  /  may  be  taken  out  through 
the  hole  closed  by  the  plug  g. 


50 


OIL  FUEL  FOR  STEAM  BOILERS 


Rapidity  in  cleaning  is  the  chief  feature  of  the  basket 
strainer  shown  in  Fig.  28.  The  device  is  installed  in  a 
horizontal  section  of  the  oil-pipe  line,  and  the  oil  flows 
through  from  a  to  b,  being  thus  forced  to  pass  through 
the  strainer  c,  which  consists  of  a  metal  basket  closed  at 
the  bottom,  perforated  on  the  sides  with  large  holes,  and 
lined  with  closely  fitting  wire  gauze  d.  The  gauze  does 
the  straining  and  the  metal  basket  simply  holds  the 
gauze  and  prevents  it  from  being  torn.  If  the  gauze  were 

not  supported  and  it  be- 
came clogged,  the  resist- 
ance it  would  offer  to  the 
passage  of  the  oil  might 
cause  it  to  be  torn.  The 
basket  has  a  rim  that  rests 
on  the  seat  e  and  the  in- 
clined ribs  /  on  the  rim  are 
locked  firmly  under  the  lugs 
g  by  giving  the  basket  a 
part  of  a  turn.  The  screw- 
down  cover  h  has  a  pair  of 
handles  i  by  which  it  may 
be  unscrewed  quickly  and 
lifted  off,  after  which  the 
basket  is  given  a  twist  to 

unlock  it  and  is  then  removed.      Packing  under  the 
flange  of  the  cover  prevents  leakage  of  oil. 

Sometimes  the  strainer  is  located  in  the  same  casting 
with  the  burner,  as  in  the  Koerting  type,  shown  in  Fig.  29. 
The  casting  0,  of  which  only  a  part  is  shown,  contains  a 
pair  of  burners,  each  of  which  is  supplied  with  oil  from  an 


FIG.  29. — Koerting  type  of  oil 
strainer. 


CLEANING  OF  OIL  FUEL  51 

oil  inlet  b  through  a  perforated  metal  strainer  c.  The 
strainer  is  cylindrical  and  fits  snugly  over  a  cylindrical 
hollow  cage  d  that  has  several  long  slots  e  in  the  sides. 
The  cage  is  screwed  into  the  casting  a,  being  inserted 
through  the  opening  made  by  removing  the  plug  /.  The 
oil  from  the  inlet  b  surrounds  the  strainer,  passes  through 
it  and  the  slots  to  the  interior  of  the  cage,  and  then  flows 
through  the  opening  g  to  the  chamber  h,  which  leads  to 
the  burner.  As  each  strainer  serves  its  own  burner  and 
the  two  are  separate,  it  is  possible  to  shut  down  one  burner 
and  remove  its  strainer  without  affecting  the  operation 
of  the  other  burner.  On  restarting  after  inserting  a  clean 
strainer,  the  burner  that  remained  working  will  ignite 
the  fresh  spray  of  fuel  from  the  other  burner.  This 
arrangement  enables  the  strainers  to  be  cleaned  without 
completely  interrupting  the  operation  of  the  burners. 

Of  course,  the  same  object  could  be  accomplished  by 
installing  a  pair  of  strainers  of  any  type,  with  the  valves 
and  piping  so  arranged  that  while  one  was  out  of  service 
for  cleaning  or  repair,  the  oil  could  be  sent  through  the 
other. 

A  special  type  of  strainer  is  illustrated  in  Figs.  30  and 
31,  which  show  two  different  positions  of  the  same  device. 
Corresponding  parts  in  both  views  are  therefore  marked 
with  the  same  reference  letters.  The  important  feature 
of  this  strainer  is  that  it  can  be  cleaned  without  taking  it 
apart  and  without  interrupting  the  flow  of  oil.  Fig.  30 
shows  a  section  of  the  strainer  in  its  normal  working  posi- 
tion. The  oil  flows  in  at  a  and  is  directed  downward  by 
the  curved  passage  b  into  the  interior  of  the  conical  per- 
forated strainer  c.  The  passage  b  is  formed  in  a  tapering 


52 


OIL  FUEL  FOR  STEAM  BOILERS 


plug  d  that  fits  closely  in  the  body  e  of  the  device,  and 
this  plug  may  be  rotated  by  means  of  the  handle  /.  The 
strainer  c  is  held  down  firmly  by  the  collar  g  on  the  lower 
end  of  the  plug.  The  oil,  after  passing  through  the  cone 
into  the  surrounding  chamber  h,  flows  upward  and  out 
at  i.  The  plug  is  held  in  place  by  the  pressure  of  the 


k 


FIGS.  30  and  31. — Two  views  of  oil  strainer  arranged  for 
cleaning  without  removal. 

plate  j  bolted  to  the  body  e,  and  packing  is  inserted  at  the 
joint  to  prevent  leakage  of  oil.  The  handle  /  has  on  its 
under  side  a  lug  that  comes  against  one  or  the  other  of 
the  lugs  k  and  I  set  90  deg.  apart  on  the  plate  j.  These 
limit  the  rotation  of  the  handle,  and  consequently  of  the 
plug,  to  a  quarter- turn. 


CLEANING  OF  OIL  FUEL  53 

When  the  strainer  becomes  so  dirty  as  to  require  clean- 
ing, the  handle /is  given  a  quarter- turn,  which  brings  the 
plug  into  the  position  shown  in  Fig.  3 1 .  There  is  a  second 
passage  m  at  right  angles  to  the  passage  b,  and  when  the 
plug  is  turned  the  oil  flows  directly  from  the  inlet  to  the 
outlet,  without  passing  through  the  strainer.  Next,  the 
blow-out  valve  n  at  the  bottom  of  the  chamber  o  is 
opened,  after  a  bucket  is  set  under  it.  Then  the  valve  p 
is  opened,  admitting  live  steam  to  the  chamber  h  from 
the  supply  pipe  q.  The  steam  rushes  through  the  cone 
in  a  direction  opposite  to  that  in  which  the  oil  flows  and 
loosens  the  dirt,  which  falls  to  the  bottom  of  the  chamber 
o.  It  is  then  blown  out  through  the  valve.  By  the  use 
of  this  strainer  there  is  no  interruption  of  the  oil  supply 
and  unstrained  oil  is  sent  to  the  burners  only  during  the 
brief  time  required  to  blow  out  the  dirt.  The  handle  / 
is  then  swung  back  to  its  first  position  and  the  strainer 
resumes  its  normal  working. 


CHAPTER  VI 
PUMPING  AND  HEATING  OF  OIL  FUEL 

In  every  oil-fuel  installation  there  must  be  pumps  to 
draw  the  oil  from  the  storage  tanks  and  deliver  it  to  the 
burners  under  pressure.  The  storage  tanks  are  invariably 
located  underground  and  therefore  at  a  lower  level  than 
the  burners.  The  primary  purpose  of  the  pumps,  conse- 
quently, is  to  lift  the  oil  from  the  tanks.  The  heavy 
oils  employed  for  fuel  are  usually  too  viscous  and  sluggish 
to  flow  freely  of  their  own  accord,  and  so  the  pumps  fulfil 
the  second  object  of  supplying  the  oil  under  pressure.  In 
this  way  the  maximum  amount  of  oil  supplied  may  be 
regulated  to  suit  the  demand,  regardless  of  the  condition 
or  quality  of  the  oil. 

One  of  the  simplest  methods  of  insuring  a  steady  pres- 
sure of  oil  at  the  burners  is  to  use  a  standpipe,  as  shown 
in  Fig.  32.  The  oil  is  drawn  from  the  storage  tank 
through  the  suction  pipe  a  by  the  pump  b  and  is  dis- 
charged through  the  pipe  c  into  the  standpipe  d.  This 
is  made  of  4-in.  pipe  and  is  of  sufficient  height  to  give 
the  desired  pressure  of  oil  at  the  burners.  An  overflow 
pipe  e  one  or  two  sizes  larger  than  the  discharge  pipe 
c  is  connected  near  the  top  and  is  carried  back  to  the 
storage  tank.  The  speed  of  the  pump  is  regulated  so  that 
the  amount  of  oil  delivered  is  somewhat  in  excess  of  that 
used  by  the  burners.  As  a  result,  the  standpipe  is 

54 


PUMPING  AND  HEATING  OF  OIL  FUEL 


55 


constantly  kept  full  to  the  level  of  the  overflow.  The 
excess  of  oil  simply  flows  back  to  the  storage  tank  through 
the  pipe  e,  and  as  the  height  of  the  oil  column  in  the 
standpipe  remains  unchanged,  the  pressure  in  the  oil 
main  /,  leading  to  the  burners,  remains  constant.  The 


FIGS.  32  and  33. — Standpipe  used  to  obtain  steady  oil  pressure 
and  safety  device  for  draining  standpipe. 


pipe  g  is  an  extension  of  the  standpipe  that  serves  as  a 
trap  for  water  and  sediment  contained  in  the  oil.  These 
impurities,  being  heavier  than  the  oil,  fall  to  the  bottom 
of  the  pipe  g  and  may  be  blown  out  at  intervals  through 
the  pipe  h.  A  vent  cock  i  is  added  at  the  top  of  the 


56  OIL  FUEL  FOR  STEAM  BOILERS 

standpipe  to  allow  the  release  of  gas  that  enters  with 
the  oil  and  collects  above  the  column. 

The  object  of  maintaining  a  uniform  pressure  of  oil 
is  to  insure  proper  working  of  the  burners  and  econon> 
ical  combustion.  If  the  pressure  were  allowed  to 
vary  rapidly,  the  rate  of  flow  of  the  oil  would  be  changed 
and  the  burners  would  work  erratically.  Not  only  that, 
but  the  ratio  of  air  to  oil  would  be  altered  continually 
and  inefficient  combustion  would  result.  There  seems 
to  be  no  fixed  value  for  the  pressure  at  which  the  oil  is 
delivered  to  the  burners.  In  an  extended  series  of  tests 
made  by  the  Bureau  of  Steam  Engineering  of  the  United 
States  Navy,  the  pressure  varied  from  9  Ib.  to  160  Ib. 
per  sq.  in.,  depending  on  the  type  of  burner,  the  quality 
of  the  oil  and  the  nature  of  the  installation.  In  the 
greater  number  of  cases,  however,  the  pressure  lies  within 
the  limits  of  10  Ib.  and  50  Ib.  per  sq.  in. 

The  required  height  of  the  column  of  oil  in  the  stand- 
pipe  to  produce  a  desired  pressure  may  easily  be  calcu- 
lated, if  the  specific  gravity  of  the  oil  is  known,  by  the 
use  of  the  formula 


p 

2.304 


in  which 


H  =  height  of  oil  column,  in  feet; 

P   =  required  oil  pressure,  in  pounds  per  square  inch; 

G   =  specific  gravity  of  oil  used. 

The  height  H  of  the  oil  column  thus  found  is  the  ver- 
tical distance  between  the  level  of  the  burner  orifices 
and  the  level  of  the  overflow  at  the  top  of  the  standpipe. 


PUMPING  AND  HEATING  OF  OIL  FUEL  57 

For  example,  if  a  pressure  of  15  Ib.  per  sq.  in.  is  required 
and  the  oil  has  a  specific  gravity  of  0.96,  the  height  of 
the  oil  column  must  be 

#  =  2.304X15-;- 0.96  =  36  ft. 

With  the  standpipe  arrangement,  a  considerable 
quantity  is  stored  at  a  point  above  the  level  of  the 
burner  outlets;  consequently,  if  a  burner  should  inad- 
vertently be  left  open  when  out  of  service,  the  furnace 
would  be  flooded  with  oil.  Because  of  this,  some  in- 
surance companies  refuse  to  insure  plants  in  which  oil 
is  fed  by  gravity. 

The  danger  of  flooding  with  oil  may  be  overcome  by 
using  a  safety  device,  so  that  when  there  is  no  steam 
pressure  for  atomizing,  the  oil  in  the  standpipe  will  be 
rpturned  to  the  storage  tank.  An  arrangement  of  this 
kind  is  shown  in  Fig.  33.  The  pipe  a,  leading  from  the 
standpipe  b  to  the  burners,  has  a  branch  c,  in  which  is 
fitted  a  cock  d  that  is  opened  when  the  weighted  lever 
e  is  allowed  to  fall.  This  lever  is  connected  by  a  chain 
/  to  the  piston  rod  g  of  a  small  piston  in  the  cylinder  h. 
A  steam  pipe  from  the  boiler  is  attached  at  i  and  a  pipe 
j  leads  to  the  oil  pump,  so  that  the  steam  supply  to  the 
pump  must  pass  through  the  cylinder  h.  The  pressure 
of  the  steam  forces  the  piston  to  the  upper  end  of  the 
cylinder  and  holds  it  there,  thus  keeping  the  cock  d 
closed  as  long  as  there  is  sufficient  pressure  in  the  boiler. 
But  when  the  steam  pressure  falls  below  that  required 
to  run  the  pump  and  atomize  the  oil,  the  lever  e  drops 
and  opens  the  cock  d,  thus  allowing  all  the  oil  in  the 
standpipe  to  run  back  into  the  storage  tank. 


58 


OIL  FUEL  FOR  STEAM  BOILERS 


Another  way  of  maintaining  a  uniform  pressure  of  oil 
is  to  employ  a  duplex  feed-pump  and  to  put  on  the  dis- 
charge pipe  a  relief  valve  set  to  open  when  the  desired 
pressure  is  exceeded.  A  side  view  of  such  an  apparatus 
is  shown  in  Fig.  34  in  connection  with  a  longitudinal 


FIG.  34. — Oil-pressure  pump  with  heater. 

section  of  an  oil  heater.  The  duplex  pump  a  has  a  suc- 
tion pipe  b  that  leads  direct  from  the  storage  tank.  The 
discharge  from  both  sides  of  the  pump  is  led  through  the 
pipe  c  to  the  heater  d.  The  air  chamber  e  and  the  relief 
valve  /  are  in  communication  with  the  discharge  pipe 


PUMPING  AND  HEATING  OF  OIL  FUEL  59 

through  the  croSs  g.  The  air  chamber  cushions  the  in- 
termittent discharges  of  oil  and  prevents  shocks.  The 
relief  valve,  which  is  merely  a  spring-loaded  valve,  is 
set  to  the  pressure  desired  at  the  oil  burners.  As  soon 
as  the  pump  supplies  too  much  oil,  and  this  pressure  is 
exceeded,  the  valve  rises  and  the  excess  of  oil  is  returned 
to  the  storage  tank  by  a  pipe  connected  at  h.  Two 
small  pipes  lead  from  the  tops  of  the  discharge  chambers 
to  the  overflow  pipe  and  are  fitted  with  valves  i  to  allow 
any  gas  collecting  in  those  chambers  to  be  removed. 

The  speed  of  the  pump  is  regulated  automatically  by 
a  governor  j  on  the  steam  line  k  to  the  pump.  The 
governor  consists  of  a  flexible  diaphragm  directly  con- 
nected to  a  throttle  valve  in  the  steam  line.  One  side 
of  the  diaphragm  is  acted  on  by  the  pressure  of  the  oil, 
which  is  transmitted  through  the  small  pipe  /,  and  on 
the  other  side  by  a  spring  that  can  be  adjusted  as  desired. 
When  the  oil  pressure  rises  too  high,  the  pressure  of  oil 
on  the  diaphragm  overcomes  the  spring  pressure  and 
closes  the  throttle  valve  somewhat.  This  reduces  the 
steam  supply  to  the  pump  and  lessens  its  speed.  The 
oil  pressure  then  decreases  and  the  spring  forces  the 
diaphragm  back  again,  opening  the  valve  and  admitting 
more  steam.  By  adjusting  the  tension  of  the  spring,  a 
very  uniform  speed  of  the  pump  may  be  obtained. 
The  exhaust  from  the  steam  ends  of  the  pump  is  led 
through  the  pipe  m  to  the  heater,  where  it  is  used  to  heat 
the  oil.  A  pressure  gage  is  attached  at  n  to  show  the 
pressure  of  the  oil  on  the  discharge  side  of  the  pump. 

The  object  of  the  heater  is  to  increase  the  temperature 
of  the  oil  and  thereby  decrease  its  viscosity.  The  heavy 


60  OIL  FUEL  FOR  STEAM  BOILERS 

crude  oils  are  very  sluggish,  and  in  this  condition  they  are 
not  easily  atomized.  If  their  temperature  is  low,  their 
rate  of  flow  is  still  further  reduced.  Therefore,  a  heater 
is  inserted  in  the  oil  system  to  render  the  oil  more  fluid 
and  easy  to  break  up  into  a  spray.  In  the  illustration 
the  heater  is  placed  between  the  discharge  of  the  pump 
and  the  burners.  It  consists  of  a  cylindrical  outer  shell 
d  into  which  the  exhaust  steam  is  conducted  by  the  pipe 
m.  The  head  o  of  the  heater  has  two  compartments, 
and  into  it  are  screwed  two  sets  of  tubes.  The  larger 
tubes  are  closed  at  one  end  and  fit  over  the  smaller  ones, 
which  are  open  at  both  ends.  The  oil  from  the  pump 
flows  into  the  inner  compartment  in  the  head,  thence 
into  the  larger  tubes,  around  the  smaller  ones,  and  finally 
back  through  the  inside  tubes  to  the  outer  compartment, 
from  which  it  passes  to  the  burners  through  the  strainer 
p.  t  The  water  and  uncondensed  steam  are  drawn  out  of 
the  shell  at  q. 

The  form  of  heater  shown  in  Fig.  34  is  efficient,  be- 
cause the  oil  is  divided  into  a  number  of  thin  films  that 
pass  between  the  outer  and  inner  tubes  while  the  heat  is 
transmitted  through  the  outer  tubes.  A  much  simpler 
form,  and  one  that  is  less  expensive,  is  shown  in  Fig. 
35.  It  consists  of  two  cast-iron  cylinders  a  and  b,  one 
inside  the  other.  The  narrow  space  c  between  the  inner 
and  outer  shells  is  filled  with  the  oil  to  be  heated,  which 
flows  in  at  d  and  out  at  e.  Steam  is  led  into  the  inside 
cylinder  through  a  pipe/,  and  the  water  and  waste  steam 
are  removed  atg.  This  form  is  not  extremely  efficient, 
because  the  cast-iron  walls  are  thick  and  the  oil  is  not 
divided  into  very  thin  sheets. 


PUMPING  AND  HEATING  OF  OIL  FUEL 


61 


Another  way  of  arranging  the  coils  in  the  heater  is 
shown  in  Fig.  36.  The  oil  flows  into  the  heater  shell  a 
through  the  pipe  b  and  surrounds  the  pipe  coils  c,  which 
are  made  up  of  straight  pipes  joined  by  return  bends. 
Steam  is  admitted  into  the  top  coil  through  the  connec- 
tion at  d,  and  the  water  is 
drained  out  at  e.  The  oil 
flows  through  the  heater 
from  b  to/. 

The  heater  shown  in  Fig. 
36  is  more  efficient  than  that 
in  Fig.  35,  but  the  one 
shown  in  Fig.  37  gives  better 
heating  than  either,  because 
the  coil  a  that  carries  the 
steam  has  a  greater  amount 
of  heating  surface  exposed 
to  the  oil.  It  is  made  in  a 
continuous  coil  that  fits 
closely  inside  the  shell  b. 

Steam  enters  at  c  and   the  condensation  escapes  at  d. 
The  oil  enters  at  e  and  is  discharged  at/. 

The  corrugated  film  heater  shown  in  Fig.  38  is  designed 
with  a  view  to  obtaining  a  very  high  efficiency.  It 
consists  of  two  spirally  corrugated  copper  tubes  a  and  b. 
These  fit  very  closely,  leaving  only  a  thin  space  between 
them,  and  oil  is  led  into  this  space  through  the  inlet  c. 
It  flows  upward  between  the  two  corrugated  tubes  and 
passes  out  at  d.  Steam  is  admitted  through  the  pipe  e 
and  flows  directly  to  the  interior  /  of  the  tube  b.  At 
the  same  time  a  branch  pipe  g  admits  steam  to  the  cham- 


FIGS.  35,  36  and  37.— Forms 
of  oil  heaters. 


62 


OH,  FUEL  FOR  STEAM  BOILERS 


FIG.  38. — Corrugated  coun- 
terflow  oil  heater. 


her  h  surrounding  the  outer 
tube  and  formed  by  the  in- 
closing cylindrical  shell  i.  The 
oil  film  is  thus  heated  by  the 
transmission  of  heat  inward 
through  the  outer  tube  and 
outward  through  the  inner 
tube.  The  steam  and  oil  flow 
in  opposite  directions,  so  that 
the  warmest  oil  meets  the  steam 
entering  the  heater.  This 
counter-current  adds  to  the 
efficiency  of  operation.  The 
drain  pipe  j  serves  to  remove 
all  condensation  from  the  steam 
chambers,  and  the  shell  is  pro- 
tected by  a  non-conducting 
covering  k  that  reduces  the  loss 
of  heat  to  the  surrounding  air. 
The  tubes  may  be  removed 
for  cleaning;  or  the  plugs  /  and 
m  may  be  taken  out  and  live 
steam  may  be  blown  through 
between  the  tubes.  This  will 
quickly  and  thoroughly  clean 
out  all  sediment  and  tarry  de- 
posits. 

As  the  heater  is  placed  be- 
tween the  pump  and  the 
burners,  it  is  subjected  to  the 
full  pressure  of  the  oil,  and  it 


PUMPING  AND  HEATING  OF  OIL  FUEL  63 

should  be  tested  to  see  that  it  is  capable  of  withstand- 
ing the  maximum  pressure  that  may  be  put  upon  it. 
Some  makers  guarantee  their  heaters  for  a  pressure  of 
200  Ib.  per  sq.  in.,  which  is  well  above  the  point  that 
will  be  reached  in  ordinary  work.  The  joints  of  the 
steam  coils  or  of  the  tubes  fitted  in  the  head  of  the  heater 
should  be  absolutely  tight,  so  that  no  water  can  leak  into 
the  oil  supply.  Also,  the  pipes  and  tubes  should  be 
arranged  so  that  they  can  expand  and  contract  freely, 
without  springing  joints  open  and  causing  leaks. 

Heating  of  the  oil  between  the  pump  and  the  burners 
is  done  to  make  atomization  easier.  In  some  cases, 
however,  it  is  necessary  to  heat  the  oil  in  the  storage 
tank  so  that  it  will  flow  readily  to  the  pump.  This  is 
particularly  true  of  installations  in  cold  climates.  There 
are  crude  oils  that  at  temperatures  of  from  30  to  40  deg. 
Fahr.  become  so  sluggish  that  they  cannot  be  drawn  to 
the  pump,  and  they  must  be  heated  sufficiently  to  cause 
them  to  flow.  It  is  neither  necessary  nor  advisable  to 
heat  the  entire  bulk  of  oil  in  the  storage  tank.  A  steam 
coil  can  be  located  around  the  lower  end  of  the  suction 
pipe.  This  will  heat  the  oil  in  the  immediate  neighbor- 
hood of  the  entrance  to  the  pipe  and  enable  it  to  be  drawn 
up.  In  any  case,  the  heating  must  not  be  carried  to  a 
point  at  which  the  oil  will  begin  to  decompose,  that  is, 
break  up  into  its  constituent  hydrocarbons.  The  tem- 
perature at  which  decomposition  occurs  varies  for  oils 
of  different  qualities  and  from  different  localities,  but 
usually  it  does  not  exceed  180  deg.  Fahr. 

The  temperature  of  the  oil  may  be  observed  by  a 
thermometer  placed  in  a  mercury  cup  in  the  oil  line 


64 


OIL  FUEL  FOR  STEAM  BOILERS 


leading  to  the  burners,  as  shown  in  Fig.  39.  The  pipe 
a  conveys  the  oil  to  the  burners,  and  into  it  is  screwed 
a  fitting  b  that  carries  the  ther- 
mometer tube  c  and  the  scale  d. 
At  the  bottom  is  a  long  cup  e  filled 
with  mercury,  in  which  the  lower 
end  of  the  tube  c  rests.  The 
heat  of  the  oil  flowing  through  the 
pipe  is  thus  transmitted  to  the 
tube  and  the  temperature  is  regis- 
tered on  the  scale. 

If  the  plant  is  of  such  character 
that  even  a  brief  shutdown  would 
entail  great  loss  or  inconvenience, 
the  oil  pump  should  be  duplicated, 
so  that  one  set  of  pumps  will  be 
in   reserve   in  case  the  other  set 
fails.     This  can   be  arranged  by 
FIG.  39.— Thermom-     using  a  system  of  cross-overs  in 
eter  for  finding  temper-     the  piping.     Also,  it  is  an  excellent 
1  in  pipe'  plan  to  have  the  entire  system  of 

oil  pipes  connected  so  that  live  steam  may  be  blown 
through  it  to  clean  it  of  dirt  and  tarry  matter  ad- 
hering to  it. 


CHAPTER  VII 

OIL-BURNING  FURNACES 

The  arrangement  of  the  furnace  of  a  boiler  that  is  to 
be  fired  with  oil  fuel  varies  according  to  the  type  of 
boiler  and  the  location  of  the  burner;  also,  it  makes  con- 
siderable difference  whether  the  boiler  setting  is  orig- 
inally planned  for  the  use  of  oil  fuel  or  whether  it  is 
altered  from  the  coal-burning  type.  Details  of  the 
arrangements  will  differ  because  of  the  manner  in  which 
the  air  supply  is  allowed  to  enter.  In  view  of  these 
facts,  it  would  manifestly  be  impossible  to  illustrate  all 
of  the  many  styles  of  furnaces,  but  several  of  them  will 
be  given  to  show  their  distinctive  features. 

A  form  of  oil-burning  furnace  for  a  return- tubular 
boiler  is  shown  in  section  and  in  plan  in  Fig.  40.  There 
is  a  single  fan-tailed  burner  a  installed  in  the  center  of 
the  fire-door.  It  projects  well  through  the  front  wall 
and  is  surrounded  by  a  short  firebrick  sleeve  or  arch  b. 
The  grates  c  are  retained,  and  on  them  is  laid  a  closely 
fitted  layer  d  of  firebrick  that  prevents  air  from  rising 
through  the  grates  except  at  the  extreme  rear  end.  On 
this  layer  of  brick  are  placed  a  number  of  blocks  that 
support  another  layer  e,  and  this  top  layer  forms  a  con- 
tinuous floor  from  the  arch  b  to  the  top  of  the  bridge 
wall  /.  The  air  supply  is  admitted  through  the  door  g 
to  the  space  beneath  the  grates,  whence  it  flows  to  the 
5  65 


66  OIL  FUEL  FOR  STEAM  BOILERS 

rear,  up  through  the  grates,  forward  between  the  fire- 
brick layers  d  and  e,  and  then  past  the  burner  into  the 


FIG.  40. — Return-tubular  boiler  with  slot  oil  burner. 

combustion  chamber,  as  indicated  by  the  small  arrows. 
The  arch  b  and  the  layer  e  of  firebrick  are  kept  at  the 
point  of  incandescence  by  the  flame  from  the  burner, 


OIL-BURNING  FURNACES 


67 


and  the  air  in  flowing  along  in  contact  with  the  hot 
brickwork  becomes  heated  to  a  high  temperature  be- 
fore it  reaches  the  tip  of  the  burner.  This  preheating 
of  the  air  supply  adds  to  the  efficiency  of  the  combus- 
tion. All  joints  or  openings  around  the  burner  are  care- 
fully closed,  so  that  no  cold  air  can  leak  into  the  furnace. 
The  entire  air  supply  must  therefore  pass  under  the 
heated  slabs  e. 


FIG.  41. — Return-tubular  boiler  with  Kirk  wood  oil  burner. 

A  return-tubular  boiler  arranged  to  use  a  Kirkwood 
burner  is  shown  in  section  in  Fig.  41.  In  this  case  the 
grate  bars  are  retained  but  are  covered  with  a  closely  laid 
floor  a  of  firebrick  that  has  a  single  slot  b  for  the  admis- 
sion of  air  to  the  furnace  from  the  ashpit.  The  burner  c 
is  set  in  firebrick  in  the  fire-door  opening  and  the  slot  it 
is  just  in  front  of  it.  The  air  on  meeting  the  oil  spray 
unites  with  it  and  the  flames  are  thrown  toward  the  rear, 
where  they  strike  the  firebrick  pier  d  built  on  the  grates. 


68 


OIL  FUEL  FOR  STEAM  BOILERS 


This  pier  is  not  solid,  but  forms  a  sort  of  checkerwork  by 
which  the  burning  gases  are  thoroughly  diffused  and 
mixed  so  as  to  prevent  the  possibility  of  incomplete 
combustion,  beyond  the  bridge  wall  the  floor  e  is 
brought  level  with  the  top  of  the  bridge  wall,  so  that 
the  hot  products  of  combustion  are  kept  in  close  contact 
with  the  boiler  shell.  With  this  arrangement  the 


FIG.  42. — Return-tubular   boiler    with  Best    oil   burner. 

flames  are  directed  against  the  firebrick  on  the  grates 
and  that  forming  the  pier,  but  not  against  the  boiler 
shell. 

The  arrangement  suggested  for  a  return-tubular  boiler 
fitted  with  a  Best  burner  is  shown  in  Fig.  42.  The  bridge 
wall  is  torn  down  until  its  top  is  level  with  the  surface  of 
the  grates.  On  this  surface  firebrick  is  laid  flat,  with  air 
spaces  about  1/2  in.  wide  in  the  part  on  the  grates.  The 
burner  is  inserted  in  an  opening  in  the  front  wall  of  the 
setting,  on  the  center  line  of  the  furnace.  Its  tip  is 


OIL-BURNING  FURNACES 


69 


about  8  in.  above  the  firebrick  on  the  grates  and  about  2 
in.  inside  the  front  wall.  The  flame  is  thrown  out  parallel 
to  the  grate  surface  and  to  the  full  width  of  the  furnace. 
The  air  supply  passes  up  through  the  openings  in  the 
brickwork  covering  the  grates  and  mixes  with  the 
vaporized  oil  at  all  parts  of  the  furnace. 


FIG.  43. — Babcock  &  Wilcox  boiler  with  burner  at  front. 


The  furnace  arrangement  shown  in  Fig.  43  is  for  a 
Babcock  &  Wilcox  water-tube  boiler.  The  grates  are 
covered  with  a  single  layer  of  firebrick  a  laid  close  to- 
gether except  at  the  front,  where  a  series  of  openings  b 
are  left.  The  burner  c,  which  throws  a  fan-shaped  flame, 
projects  through  the  fire-door  and  its  tip  is  just  inside 
the  front  wall.  Thus  the  flame  from  the  burner  is  directly 


70  OIL  FUEL  FOR  STEAM  BOILERS 

above  the  openings  b  in  the  brickwork.  The  air  supply 
in  this  case  is  not  preheated  to  any  great  extent,  because 
it  flows  into  the  ashpit  through  the  door  d  and  passes 
immediately  to  the  combustion  chamber  through  the 
openings  in  the  grates.  The  slot  in  the  end  of  the  burner 
is  horizontal,  and  the  sheet  of  flame  thus  produced  is 
practically  parallel  to  the  surface  of  the  grates. 

The  arrangement  shown  in  Fig.  44  is  also  for  a  Babcock 
&  Wilcox  boiler.  It  differs  markedly  from  that  pre- 
viously illustrated  in  that  the  burners  are  located  at  the 
back  of  the  furnace,  against  the  bridge  wall,  instead  of 
at  the  front.  The  grates  are  removed  completely  and  a 
firebrick  floor  a  is  built  to  cover  the  entire  area  from  the 
front  wall  to  the  bridge  wall.  As  may  be  seen  in  the  plan 
view,  this  floor  is  carried  by  the  side  walls  of  the  furnace 
and  by  the  three  sets  of  bearing  bars  b  that  rest  on  the 
side  walls  and  on  two  longitudinal  piers.  The  burners 
c  are  set  in  recesses  in  the  front  face  of  the  bridge  wall, 
just  above  the  level  of  the  floor,  and  are  of  the  Hammel 
type.  They  direct  fan-shaped  flames  forward  over  the 
flat  floor  a.  The  three  passages  formed  beneath  the 
bearing  bars  contain  the  oil  and  steam  pipes  leading  to 
the  burners  and  also  serve  as  air  ducts  by  which  the  air 
supply  is  led  to  the  burners.  Inasmuch  as  the  floor  a 
is  kept  incandescent,  the  air  flowing  along  beneath  it  is 
heated  hignly  before  being  allowed  to  flow  upward  past 
the  burner  into  the  furnace. 

The  three  transverse  rows  of  firebrick  just  in  front  of 
the  burners  are  not  laid  end  to  end,  but  small  spaces  are 
left,  in  order  that  some  of  the  air  may  rise  directly 
through  these  openings  and  mingle  with  the  oil  vapor 


OIL-BURNING  FURNACES 


71 


above  the  floor.  This  is  done  to  prevent  carbon  from 
being  deposited  on  the  brickwork  just  below  the  tips  of 
the  burners.  To  the  remainder  of  the  floor  a  a  coating  of 


FIG.  44. — Babcock  &  Wilcox  boiler  with  burner  at  bridge  wall. 

fireclay  wash  is  given  to  fill  up  all  joints  and  prevent  air 
from  flowing  up  through  except  as  provided  by  the  slots. 
The  passage  for  each  burner  is  separate  from  the  others, 


72  OIL  FUEL  FOR  STEAM  BOILERS 

and  the  air  supply  to  each  burner  can  therefore  be  regu- 
lated by  the  ashpit  door,  independently  of  the  others. 

The  object  to  be  gained  by  placing  the  burners  at  the 
bridge  wall  and  directing  the  flames  forward  is  a  better 
utilization  of  the  combustion  space.  When  the  air  and 
the  gasified  fuel  unite  and  burn,  the  heat  generated 
causes  the  temperature  of  the  gases  to  rise,  and  they  ex- 
pand in  volume  as  a  consequence.  By  having  them 
projected  toward  the  front  of  the  furnace,  where  the  area 
of  vertical  cross-section  is  greater  because  of  the  upward 
slant  of  the  tubes,  the  increased  volume  of  the  gases  is 
accommodated  by  the  increased  space  and  the  rate  of  flow 
of  the  products  of  combustion  is  thus  rendered  more 
nearly  uniform.  It  will  be  observed  that  the  front  wall 
of  the  furnace  is  protected  from  the  heat  of  the  flames 
by  a  firebrick  lining. 

A  form  of  furnace  construction  used  in  connection  with 
a  Heine  water- tube  boiler  is  shown  in  Fig.  45.  The 
bridge  wall  is  torn  out  completely  and  the  whole  floor  is 
brought  to  the  level  of  the  bottom  of  the  ashpit.  On  this 
surface  two  layers  of  firebrick  are  placed,  as  at  a  and  b, 
separated  by  bricks  c  laid  on  edge  and  so  supported  as  to 
leave  an  air  passage  d  underneath  the  lower  layer.  The 
air  supply  enters  through  the  ashpit  doors,  flows  to  the 
back  end  of  the  boiler  through  the  passage  d,  then  for- 
ward between  the  layers  a  and  b,  and  escapes,  highly 
heated,  into  the  furnace  just  beneath  the  burner  e.  The 
burner  is  of  the  slot  type  and  throws  a  fan-shaped  flame 
that  spreads  to  the  sides  of  the  furnace.  The  inclination 
of  the  burner  is  such  that  the  flame  is  about  parallel  to  the 
rows  of  tubes. 


OIL-BURNING  FURNACES 


73 


The  Stirling  water- tube  boiler  arranged  for  burning  oil 
with  a  Best  burner  is  shown  in  section  in  Fig.  46.  The 
grates  are  removed  and  the  sloping  floor  of  the  furnace 
is  covered  with  firebrick  laid  flat  in  rows  9  in.  from  center 
to  center.  On  top  of  this  firebricks  are  laid  on  edge  and 
9  in.  from  center  to  center.  The  top  layer  of  firebrick  is 
laid  flat,  with  i/4-in.  air  spaces;  thus  the  air  supply  is  ad- 


FIG.  45. — Heine  boiler  with  preheating  of  air  supply. 

mitted  over  the  whole  bottom  of  the  furnace  after  being 
heated  by  contact  with  the  brickwork.  The  burner  a  is 
inserted  through  the  front  wall  about  8  in.  above  the  grate 
and  parallel  thereto,  the  tip  extending  into  the  furnace 
about  2  in.  Over  the  tip  is  constructed  a  firebrick  arch  b 
forming  an  igniting  chamber.  The  arch  is  brought  to  in- 
candescence by  the  heat  of  the  flame,  and  in  case  the  ac- 
tion of  the  burner  is  momentarily  interrupted,  as  by  a  slug 


74 


OIL  FUEL  FOR  STEAM  BOILERS 


of  water  carried  over  with  the  oil,  the  spray  will  be  reig- 
nited  by  the  hot  brickwork  when  the  burner  continues  its 
operation.  The  bridge  wall  is  constructed  with  a  fire- 
brick facing  and  a  flared  top,  so  that  the  flames  striking 


FIG.  46. — Stirling  boiler  with  auxiliary  air  duct. 

into  the  pocket  thus  formed  are  turned  back  on  them- 
selves. This  is  done  to  prevent  the  flames  from  striking 
directly  against  the  tubes.  An  auxiliary  air  "duct  c  is 
formed  in  the  bridge  wall.  It  connects  with  the  passages 


OIL-BURNING  FURNACES 


75 


beneath  the  furnace  floor  and  admits  air  to  the  upper  part 
of  the  flame  when  the  fires  are  being  forced.  At  such  a 
time  there  is  a  tendency  to  form  carbon  monoxide  at  the 
top  of  the  flame,  and  the  air  admitted  through  the  duct  c 
supplies  the  oxygen  required  to  convert  this  to  dioxide. 
The  arch  d  is  retained  and  serves  to  deflect  the  gases  to- 
ward the  front  bank  of  tubes. 

If  desired,  the  burner  can  be  put  at  the  rear  end  of  the 
furnace,  as  in  Fig.  47.     The  arrangement  in  this  case  is 


FIG.  47. — Stirling  boiler  with  burner  at  back  of  furnace. 

like  that  for  the  Babcock  &  Wilcox  boiler  fired  from  the 
rear.  The  air  ducts  are  formed  beneath  the  floor,  there 
being  one  for  each  burner,  and  the  burners  are  protected 
somewhat  by  being  set  in  recesses  in  the  bridge  wall.  The 
arch  over  the  furnace  is  omitted,  and  the  front  wall  is 
heavily  protected  with  firebrick. 

One  way  of  altering  the  usual  furnace  construction  of 
the  Stirling  boiler  so  as  to  adapt  it  to  the  use  of  oil  fuel 
is  shown  in  Fig.  48.  The  rear  half  of  the  grate  is  removed 
and  a  brick  pier  a  is  substituted.  A  firebrick  floor  b  is 


76 


OIL  FUEL  FOR  STEAM  BOILERS 


built  over  the  top  of  the  pier  and  the  remainder  of  the  grate 
surface,  and  air  spaces  from  1/4  in.  to  1/2  in.  wide  are  left 
between  the  bricks  on  the  grates.  The  arch  usually 
found  inside  the  furnace,  above  the  fire-door,  is  removed 
entirely,  because  the  burner  c  is  installed  at  about  the 
height  of  the  top  of  this  arch.  The  burner  is  of  the  slot 
type  and  is  inclined  so  as  to  project  the  flames  downward 
into  the  angle  or  pocket  formed  by  the  firebrick  floor  b 


•$$%$$$'/•-  , 

FIG.  48. — Stirling  boiler  with  burner  set  high  at  front. 

and  the  bridge  wall  d.  The  flames  thus  are  given  a  re- 
bound before  they  enter  the  first  pass  among  the  tubes. 
The  air  enters  through  the  space  below  the  grates  and 
flows  up  through  the  space  in  the  brickwork  into  the 
furnace. 

From  an  examination  of  the  settings  that  have  thus  far 
been  described  the  following  conclusions  may  be  drawn: 
The  furnace  of  an  oil-fired  boiler,  particularly  in  those 
parts  against  which  the  flames  strike,  must  be  lined  with  a 
good  quality  of  firebrick  so  as  to  protect  the  outer  walls 
and  the  boiler  and  to  resist  the  high  temperatures  pro- 


OIL-BURNING  FURNACES  77 

duced.  There  should  be  a  combustion  chamber  of  ample 
size,  in  which  the  gases  and  the  air  may  meet  and 
commingle  thoroughly,  so  that  combustion  may  be  com- 
plete before  the  resulting  products  of  combustion  are 
brought  against  the  comparatively  cool  boiler  surfaces. 
If  combustion  is  not  completed  before  the  gases  strike  the 
metal  parts  of  the  boiler,  the  consequent  chilling  will  pre- 
vent further  combustion  and  cause  smoke  to  be  formed. 
If  it  seems  likely  that  the  flames  will  strike  the  boiler, 
baffles  or  arches  should  be  set  up  to  prevent  direct  con- 
tact. This  is  particularly  necessary  in  the  case  of  the 
blow-off  pipe  of  a  return-tubular  boiler,  when  the  blow- 
off  is  carried  straight  down  through  the  gas  passage  at  the 
rear  end  of  the  boiler.  It  is  advisable  to  preheat  the  air 
supply  before  admitting  it  to  the  furnace. 

Oil  fuel  is  used  as  an  auxiliary  to  coal  in  some  cases. 
In  one  electric  power  station  oil  burners  are  installed 
with  the  idea  of  helping  out  on  peak  loads  and  for  the 
purpose  of  banking  the  boilers.  The  arrangement  of 
the  furnace  of  one  of  the  boilers  is  shown  in  Fig.  49.  At 
the  front  there  are  the  usual  grates  a  on  which  coal 
fires  are  carried  for  the  normal  operation  of  the  boilers. 
Behind  the  bridge  wall  b  the  burners  are  installed,  as 
shown  at  c.  The  combustion  chamber  for  the  oil  is 
formed  by  the  baffle  d,  the  floor  e,  the  wall  /,  and  the 
side  walls  of  the  setting.  After  combustion,  the  hot 
gases  from  the  oil  burner  pass  forward  over  the  bridge 
wall  and  travel  along  with  the  gases  rising  from  the 
grates.  The  air  supply  to  each  burner  is  admitted 
through  the  passage  g  that  contains  the  steam  and  oil 
pipes. 


78  OIL  FUEL  FOR  STEAM  BOILERS 

By  this  arrangement  it  is  possible  to  fire  the  boiler 
at  both  ends,  using  coal  and  oil  at  the  same  time.  The 
result  is  the  same  as  would  be  obtained  by  increasing  the 
rate  of  combustion  with  coal  alone;  that  is,  the  steaming 


FIG.  49. — Coal-burning  boiler  with  oil  used  for  banking  and  peak 

loads. 

capacity  of  the  boiler  is  greatly  increased.  Of  course, 
the  oil  burners  are  used  to  supply  the  additional  steam 
demanded  by  a  peak  load.  Under  normal  load  the  coal 
fires  only  are  used;  but  as  soon  as  a  sudden  increase  of 


OIL-BURNING  FURNACES  79 

load  comes  on,  the  oil  burners  are  put  in  action,  and  in  a 
very  short  time  the  capacity  is  equal  to  the  increased 
demand.  This  rapidity  of  response  to  sudden  changes 
of  load  forms  one  of  the  strongest  advantages  of  oil  fuel. 
By  adopting  the  scheme  here  outlined  the  boiler  horse- 
power may  be  increased  two-thirds,  without  increasing 
the  number  of  boilers. 

During  periods  when  the  load  is  light  oil  is  used  to 
bank  the  boilers.  There  are  four  burners  to  each  boiler, 
and  one  of  these  is  connected  so  that  it  can  be  operated 
independently  of  the  others  when  the  boilers  are  to  be 
b  anked.  At  this  particular  plant  the  oil  costs  more  per 
heat  unit  than  the  coal;  yet  it  is  found  more  economical 
to  use  oil  for  banking,  because  the  combustion  is  more 
efficient  with  the  oil  than  with  the  slow  coal  fire. 


CHAPTER  VIII 

INSTALLATION  or  OIL  BURNERS 

When  installing  oil  burners  the  piping  should  be  pro- 
vided with  unions  near  the  burners,  to  facilitate  the  work 
of  taking  them  down  when  they  must  be  repaired.  This 
point  is  very  clearly  illustrated  in  Fig.  50,  which  shows 
the  piping  for  a  Gem  burner  a.  The  oil  flows  to  the 
burner  through  the  valve  b  and  the  connecting  pipes, 


FIG.   50. — Piping  for  Gem  oil  burner. 

and  the  steam  for  atomizing  is  admitted  through  the 
valve  c  and  the  branch  to  which  it  is  fitted.  The  unions 
d  and  e  enable  the  burner  to  be  detached  from  the  sys- 
tem very  easily  and  quickly.  The  plug/,  when  removed, 
allows  the  connection  to  be  cleaned  out.  The  valve  b 
is  closed,  and  a  cap  is  placed  over  the  end  of  the  burner 

80 


INSTALLATION  OF  OIL  BURNERS  81 

so  that  the  steam  will  back  up  in  the  burner  and  blow 
back  through  the  oil  connection,  cleaning  it. 

The  pipe  connections  for  a  Best  burner  are  shown  in 
Fig.  51  in  a  diagrammatic  way.  The  burner  is  located 
at  a  and  the  oil  and  steam  lines  are  attached  on  opposite 
sides.  There  are  unions  b  and  c  to  facilitate  the  re- 
moval of  the  burner  and  stop  valves  d  and  e  for  oil  and 
steam  respectively.  In  addition,  there  is  an  oil-regulat- 
ing cock  /  between  the  stop  valve  d  and  the  burner,  to 
enable  the  flow  of  oil  to  be  regulated  with  great  precision. 


FIG.  51. — Piping  and  oil-regulating  cock  for  Best  burner. 

An  end  view  and  a  vertical  section  of  the  regulating 
cock  are  shown  in  Fig.  52.  It  consists  of  a  conical  plug 
a  that  fits  a  conical  seat  in  the  body  b  of  the  cock  and 
that  is  held  snugly  in  place  by  the  upward  pressure  of 
the  spring  c.  The  spring  is  kept  in  position  by  the  ex- 
tension d  on  the  bottom  of  the  plug  and  by  the  cap  e. 
The  latter  can  be  unscrewed  so  as  to  allow  the  plug  and 
the  spring  to  be  removed  from  .the  body  of  the  cock. 
The  oil  flows  through  a  triangular  opening  /  in  the  plug. 
The  opening  is  made  triangular  in  form  so  as  to  insure 
close  regulation  of  the  oil.  The  opening  g  in  the  body 
of  the  cock  on  the  outlet  side  of  the  plug  is  rectangular 
in  shape  and  the  outline  of  this  opening  is  dotted  around 
the  opening  in  the  plug.  By  turning  the  plug  slowly, 


82 


OIL  FUEL  FOR  STEAM  BOILERS 


the  amount  by  which  the  triangular  opening  overlaps 
the  edge  of  the  rectangular  outlet  can  be  varied  very 
gradually,  thus  giving  close  adjustment  of  the  oil  supply 
to  the  burner.  The  packing  h  around  the  stem  of  the 
plug  is  compressed  under  the  screw  cap  i  and  prevents 
leakage  of  oil  around  the  stem. 

The  cock  is  opened  fully  or  closed  completely  by  giving 
the  handle  j  a  quarter-turn.  There  is  a  lug  k  on  the 
handle,  and  it  comes  against  a  stop  /  cast  on  the  body  of 


FIG.  52. — Oil-regulating  cock. 

the  cock  when  the  plug  is  turned  to  the  closed  position- 
Also,  there  is  a  knurled  screw  m  in  a  bracket  n  fastened 
to  the  body  of  the  cock.  When  the  plug  is  turned  to 
open  the  cock,  the  lug  o  comes  against  the  point  of  the 
screw  and  the  handle  can  be  turned  no  farther.  The 
screw  can  be  adjusted  to  give  any  desired  amount  of 
opening  of  the  cock,  and  the  cock  can  be  opened  and  set 
instantly  to  this  position.  The  bracket  n  is  hinged,  and 
if  the  cock  is  to  be  opened  to  its  full  extent,  the  bracket  is 


INSTALLATION  OF  OIL  BURNERS  83 

simply  swung  upward  and  backward,  taking  the  stop 
screw  m  out  of  the  way  of  the  lug  o. 

A  form  of  valve  for  regulating  the  flow  of  oil  with 
extreme  nicety  is  shown  partly  in  section  in  Fig.  53. 
The  inner  end  of  the  valve  stem  carries  a  hollow  cylinder 
a  that  fits  snugly  in  a  circular  hole  in  the  seat  b.  In  the 
side  of  the  cylinder  is  cut  a  triangular  opening  c,  so  that, 
when  the  stem  is  screwed  out,  the  point  of  the  triangular 
opening  rises  above  the  face  d  of  the  seat  and  allows  the 
oil  to  pass  through.  The  higher  the  stem  is  drawn,  the 
greater  is  the  amount  of  opening. 

Owing  to  the  penetrative  nature  of  oil  fuel,  the  piping 
should  be  carefully  put  together  and  all  joints  should  be 
tight.  In  making  up  the  connections  the  pipe  threads 
should  be  perfect  and  should  be  cut  in  oil,  so  as  to  be 
smooth  and  free  from  cracks.  If  the  threaded  end  is 
made  too  long  the  pipe  will  screw  into  the  fitting  too 
easily  and  leakage  may  result.  It  is  better  to  cut  the 
threads  so  that  it  will  require  a  considerable  force  on 
the  pipe  wrench  to  put  the  pipes  together,  as  this  will 
be  more  apt  to  give  tight  joints. 

The  pipes  leading  to  and  from  the  storage  tank  are 
usually  permanent  and  are  not  likely  to  be  taken  apart, 
so  the  joints  may  be  made  up  with  a  cement  of  litharge 
and  glycerine  to  insure  tightness.  If  it  is  possible  to  do 
so,  elbows  should  be  avoided  in  installing  the  oil  piping, 
as  the  foreign  matter  in  the  oil  will  collect  at  these  fittings 
and  eventually  clog  the  pipes.  It  is  preferable  to  em- 
ploy bends  of  long  radius  instead  of  elbows.  It  will  be 
found  advisable  to  arrange  the  piping  in  such  a  way  that 
the  oil  can  be  turned  off  and  live  steam  sent  through  the 


84 


OIL  FUEL  FOR  STEAM  BOILERS 


oil  lines  to  loosen  the  deposits  of  asphalt  or  tarry  matter 
and  blow  them  out  of  the  pipes. 

The  proportions  of  the  furnace  and  the  style  of  oil 
burner  to  be  used  will  govern  the  number  of  burners  that 
must  be  supplied  in  a  given  installation.  To  illustrate, 
if  a  furnace  is  long  and  narrow,  a  single  burner  giving 
a  long,  conical  flame  will  be  sufficient;  but  if  the  furnace 
is  short  and  narrow,  a  single  fan-tailed  burner  will  give 


FIGS.  53  and  54. — Oil-regulating  valve  and  arrangement  for  finding 
amount  of  steam  used  by  burners. 


the  desired  results.  In  case  the  furnace  is  wide,  two  or 
more  burners  may  have  to  be  installed.  Some  makes 
of  burners  are  so  constructed  that  they  can  be  made  to 
throw  a  long,  narrow  flame  or  a  short,  wide  one.  It 
may  be  said  that,  as  a  rule,  one  burner  for  each  6  ft.  or 
7  ft.  of  width  of  furnace  will  be  required.  The  capacity 
of  the  burner  must  also  be  taken  into  account.  One 


INSTALLATION  OF  OIL  BURNERS  85 

manufacturer  guarantees  a  capacity  of  from  5  to  350 
boiler-hp.  with  a  single  size  and  type  of  burner.  Another 
rates  his  burners  at  from  75  to  100  boiler-hp.  each.  Still 
others  manufacture  different  sizes  of  burners  of  the  same 
type,  each  size  corresponding  to  a  certain  capacity. 

The  location  of  the  burner  is  a  matter  that  cannot  well 
be  considered  apart  from  the  furnace  arrangement.  In 
the  case  of  the  return-tubular  boiler,  it  is  common  to  find 
a  burner  in  the  center  of  each  fire-door;  but  if  sufficient 
capacity  can  be  obtained  by  the  use  of  a  single  burner  it 
may  be  inserted  through  an  opening  between  the  fire- 
doors,  cut  through  the  boiler  front  and  the  front  wall  of  the 
furnace.  Whatever  the  location  of  the  burner  or  burners, 
the  furnace  space  should  be  utilized  as  far  as  possible. 
This  is  one  reason  why  it  is  found  advisable  in  some  in- 
stances to  locate  the  burners  at  the  rear  end  of  the  fur- 
nace in  inclined-tube  water-tube  boilers. 

The  importance  of  supplying  dry  steam  for  atomizing 
cannot  be  overestimated.  A  steady  white  flame  is  pro- 
duced if  the  steam  is  dry;  but  if  water  is  carried  along 
with  the  steam  the  burner  sputters  and  combustion  is  re- 
tarded. The  presence  of  water  in  the  steam  may  be  due 
to  priming  of  the  boiler  or  to  condensation  in  the  pipe  line 
leading  to  the  burner.  One  way  of  avoiding  such  mois- 
ture is  to  superheat  the  steam,  which  can  be  done  very 
easily  by  running  the  steam  pipe  from  the  boiler  to  the 
burner  through  the  furnace  or  the  boiler  breeching. 
Such  an  arrangement,  however,  is  not  always  convenient. 
It  is  advisable,  then,  to  put  a  steam  separator  on  the 
steam  line  near  the  burner,  in  which  the  steam  will  be 
freed  of  its  moisture.  This  is  accomplished  by  an 


86  OIL  FUEL  FOR  STEAM  BOILERS 

abrupt  change  in  the  direction  of  flow  of  the  steam,  by 
centrifugal  force  set  up  during  a  whirling  motion  caused 
by  spiral  guides  or  vanes,  or  by  the  separating  action  of 
baffle  plates.  The  moisture  collecting  in  the  bottom  of 
the  separator  may  be  removed  through  a  drip  or  by  an 
automatic  trap. 

The  economy  of  a  burner  is  measured  by  the  amount  of 
steam  it  uses  to  atomize  a  pound  of  oil.  There  are  sev- 
eral ways  of  determining  this,  but  the  simplest  way  is  to 
condense  the  steam  that  issues  from  the  burner  in  a  given 
time,  weigh  it,  and  compare  it  with  the  amount  of  oil 
used  in  an  equal  period.  A  tank  of  cold  water  is  set  on 
scales  and  weighed  accurately.  Then  the  burner,  with 
the  same  piping  and  connections  as  are  used  in  ordinary 
operation,  is  submerged  in  the  tank.  The  steam  valve  is 
then  opened  to  the  same  extent  as  during  the  normal 
working  of  the  burner  and  is  left  open  for  a  definite  time, 
say,  a  quarter  of  an  hour. 

The  steam  escaping  from  the  burner  will  condense  in  the 
water  in  the  tank,  increasing  the  amount  of  water  and  the 
temperature.  At  the  end  of  the  given  time  the  burner  is 
removed  and  the  tank  and  its  contents  are  weighed  again. 
The  increase  of  weight  represents  the  amount  of  steam 
used  in  the  observed  time.  The  accuracy  of  the  test  may 
be  checked  by  taking  the  initial  and  final  temperatures  of 
the  water  in  the  tank  and  calculating  how  much  steam  at 
the  usual  working  pressure  would  be  required  to  produce 
the  observed  rise  of  temperature  in  the  known  weight  of 
water.  This  result  should  agree  fairly  well  with  the  in- 
crease of  weight  of  the  water  in  the  tank.  The  amount  of 
oil  used  in  the  same  length  of  time  can  be  calculated  from 


INSTALLATION  OF  OIL  BURNERS  87 

the  readings  of  the  telltale  on  the  tank,  or  from  the  read- 
ings of  the  meter  on  the  oil  line,  if  there  is  one  installed. 

This  method  is  very  simple  and  the  apparatus  is  com- 
monly available;  but  there  is  the  disadvantage  that  during 
the  test  the  burner  does  not  operate  under  the  same  condi- 
tions as  in  service.  When  the  burner  is  atomizing  oil  the 
issuing  steam  meets  the  resistance  of  the  viscous  oil  in 
the  mixing  chamber  or  at  the  orifice,  whereas  in  the  test- 
ing tank  the  resistance  is  due  to  the  water.  These  resist- 
ances differ  more  or  less,  and  the  greater  the  difference 
the  greater  the  error  in  basing  the  economy  of  the  bur- 
ner on  the  results  of  the  test.  It  is  probable  that  the 
water  will  offer  less  resistance  than  the  oil,  so  that  the 
test  will  show  the  burner  less  economical  in  steam  than 
it  really  is. 

A  more  nearly  accurate  test  may  be  made  by  using  the 
apparatus  shown  in  Fig.  54.  The  vertical  pipe  a  leads  to 
the  burners  and  conveys  the  steam  for  atomizing.  Be- 
tween the  two  flanges  b  on  this  pipe  is  a  thin  plate  in  the 
center  of  which  a  hole  3/8  in.  in  diameter  is  drilled.  The 
steam  flows  through  this  orifice  in  the  plate  on  its  way  to 
the  burners.  On  opposite  sides  of  the  flanges  the  pipes 
c  and  d  are  connected,  leading  to  the  steam-pressure 
gages  e  and/.  The  gages  register  the  steam  pressures  on 
opposite  sides  of  the  orifice  in  the  plate,  and  these 
pressures  vary  according  to  the  amount  of  opening  of  the 
steam  valve,  and  hence  according  to  the  rate  of  flow  of 
steam.  A  series  of  tests  are  made  with  different  openings 
of  the  steam-regulating  valve,  observing  the  pressures  on 
the  gages  and  catching  and  condensing  the  steam  in  a 
weighing  tank  filled  with  cold  water.  In  this  way  a 


88  OIL  FUEL  FOR  STEAM  BOILERS 

table  is  made  up  showing  the  amount  of  steam  flowing 
through  the  plate  in  a  given  time  for  each  different  com- 
bination of  pressures.  After  such  a  table  is  once  com- 
piled the  steam  consumption  of  the  burners  at  any  time 
may  be  found  quickly  by  observing  the  pressures  regis- 
tered by  the  gages  and  then  noting  the  corresponding 
steam  rate  in  the  table. 


CHAPTER  IX 

STORAGE  OF  OIL  FUEL 

The  method  of  storing  the  supply  of  oil  for  an  oil- 
burning  boiler  plant  is  a  matter  to  which  careful  con- 
sideration should  be  given.  The  objects  that  should 
be  kept  in  mind  while  planning  the  storage  system  are 
safety  and  capacity. 

For  the  average  boiler  plant  of  small  or  medium  size 
the  oil  supply  is  usually  stored  in  cylindrical  steel  tanks 
like  that  shown  in  Fig.  55.  The  tank  is  built  up  of  steel 
plates,  has  dished  ends  and  is  usually  buried  in  the 
ground  at  such  a  level  that  its  top  is  below  the  level  of 
the  tips  of  the  burners.  The  object  of  this  arrangement 
is  to  prevent  flooding  of  the  furnaces  or  of  the  boiler 
room  with  oil  in  case  a  burner  valve  is  accidentally  left 
open;  for  with  the  tanks  below  the  level  of  the  burners 
the  oil  will  flow  back  by  gravity  if  a  valve  is  left  open  at 
the  burners.  As  the  tank  is  usually  covered  with  earth, 
it  should  have  a  good  coat  of  tar  or  some  protective  paint 
to  enable  it  to  resist  the  effects  of  dampness. 

The  common  sizes  of  oil  tanks  for  boiler  installations 
are  8  ft.  in  diameter  by  28  ft.  long  and  9  ft.  in  diameter 
by  33  ft.  long.  The  former  has  a  capacity  of  about 
10,500  U.  S.  gallons  and  the  latter  a  capacity  of  approxi- 
mately 15,700  U.  S.  gallons.  In  either  case,  a  good 

89 


90 


OIL  FUEL  FOR  STEAM  BOILERS 


quality  of  steel  plate  5/16  in.  thick  should  be  used,  and 
the  heads  should  be  made  of  3/8-in.  plate. 

There  should  be  no  openings  in  the  bottom,  sides  or 
ends  of  the  storage  tank.  Such  openings  as  are  required 
should  be  at  the  top.  The  largest  opening  required  is 
that  for  the  manhole,  as  at  a,  Fig.  55,  and  this  should  be 
fitted  with  a  screw-down  cover.  There  must  be  a 
flange  b  for  connecting  the  suction  pipe  c  that  leads  to 
the  pump,  and  another  d  for  the  overflow  pipe  e,  leading 
back  from  the  standpipe  or  from  the  pressure  pumps. 


d    b 


FIG.  55. — Oil-storage  tank  with  connections. 

The  filling  pipe  /,  by  which  the  oil  is  run  into  the  tank 
from  the  tank  car,  may  be  attached  by  a  T  to  the  over- 
flow pipe  and  both  connected  with  the  tank  through  the 
nipple  g  and  the  flange  d.  Again,  there  must  be  a  flange 
h  to  which  a  ventilating  pipe  can  be  connected.  If  the 
oil  around  the  end  of  the  suction  pipe  must  be  heated,  so 
that  it  will  flow  readily  to  the  pumps,  then  it  will  be 
necessary  to  add  two  more  flanges  for  the  pipes  that 
convey  the  live  steam  and  carry  off  the  condensation. 
The  work  of  designing  and  constructing  the  tank 


STORAGE  OF  OIL  FUEL  91 

should  be  put  in  the  hands  of  a  manufacturer  familiar 
with  the  requirements  of  steam-boiler  construction,  be- 
cause the  tank  must  be  absolutely  oil-tight.  All  petro- 
leum oils  are  very  penetrative  in  their  character,  and  if 
there  is  any  suspicion  of  looseness  at  the  seams  or  around 
the  rivets,  the  oil  will  find  its  way  through.  For  this 
reason  the  rivet  holes  should  be  drilled,  or  else  punched 
and  reamed,  and  the  seams  should  be  thoroughly  calked. 

The  capacity  of  the  tank  or  tanks  installed  depends 
on  the  size  of  the  plant  and  the  frequency  with  which 
shipments  of  fuel  may  be  delivered.  If  the  plant  lies 
fairly  close  to  the  oil  fields,  so  that  there  is  little  delay 
in  obtaining  fresh  shipments,  it  is  unnecessary  to  carry 
a  large  supply  in  storage,  and  the  tank  or  tanks  may  be 
made  of  such  size  as  to  hold  oil  enough  to  run  the  plant 
for  a  week.  A  tank  9  ft.  in  diameter  and  33  ft.  in  length 
will  contain  one  week's  supply  of  oil  for  a  plant  of  500 
boiler-hp.  operating  ten  hours  a  day  at  an  average  effi- 
ciency of  75  per  cent. 

If  the  plant  is  so  located  that  shipments  of  oil  may  be 
delayed  and  cannot  be  relied  on  to  arrive  with  regularity, 
it  may  be  necessary  to  provide  storage  capacity  for  a 
month  or  more  of  continuous  working,  so  as  to  make 
reasonable  provision  against  the  possibility  of  a  complete 
shut-down. 

The  location  of  the  storage  tanks  must  be  carefully 
considered,  in  order  to  conform  to  the  requirements  of 
the  underwriters.  For  example,  if  the  tank  is  placed 
above  the  ground  level,  it  must  be  situated  at  least  200 
ft.  from  inflammable  property,  so  as  to  minimize  the 
danger  to  that  property  in  case  the  oil  should  catch  fire. 


92  OIL  FUEL  FOR  STEAM  BOILERS 

In  the  case  of  a  plant  located  in  a  town  or  a  city,  this 
requirement  would  be  hard  to  meet,  owing  either  to 
the  difficulty  of  finding  available  storage  space  or  to  the 
high  cost  of  such  space.  On  this  account,  storage 
tanks  are  usually  placed  underground.  The  require- 
ments for  an  underground  tank  are  that  it  must  be  at 
least  30  ft.  from  the  nearest  building  and  that  it  must  be 
at  least  2  ft.  below  the  surface  of  the  ground.  In  either 
form  of  installation  the  top  of  the  tank  must  be  below 
the  level  of  the  lowest  pipe  in  the  oil  system,  so  that  the 
plant  cannot  be  flooded  with  oil. 

For  ease  in  filling,  the  storage  tank  should  be  near  the 
railway  siding  on  which  the  tank  cars  are  run,  and  at 
a  lower  level,  so  that  the  oil  may  be  run  from  the  tank 
cars  into  the  storage  tank'by  gravity.  This  is  the  least 
expensive  method  of  making  the  transfer.  If  »the  tank 
is  not  at  a  low  enough  level  to  allow  this  method  of  filling 
to  be  used,  the  oil  may  be  pumped  out  of  the  tank  car 
into  the  tank,  the  suction  pipe  extending  into  the  tank 
car  and  the  discharge  pipe  being  connected  to  the  filling 
pipe  of  the  storage  tank. 

Air  pressure  has  been  used  as  a  substitute  for  pumping 
in  some  instances.  The  method  by  which  it  is  employed 
is  shown  in  Fig.  56,  in  which  a  represents  the  central 
part  of  the  tank  car.  Two  pipes  b  and  c  are  connected 
to  the  dome  d.  The  former  is  short  and  extends  only 
a  little  distance  into  the  dome.  The  other  is  long  enough 
to  reach  to  the  bottom  of  the  tank  car  and  is  connected 
to  the  filling  pipe  of  the  storage  tank.  All  ether  outlets 
from  the  tank  car  are  kept  closed,  and  compressed  air 
is  admitted  through  the  pipe  b.  The  pressure  of  the  air 


STORAGE  OF  OIL  FUEL 


93 


VOTS  uo  u   crv- 

FIGS.  56,  57,  and    58. — Arrangement    for    emptying    tank    car; 
simple  form  of  vent  pipe;  vent  pipe  and  telltale. 


94  OIL  FUEL  FOR  STEAM  BOILERS 

on  the  surface  of  the  oil  forces  the  oil  up  the  pipe  c  and 
over  into  the  storage  tank. 

It  is  stated  that  tank  cars  are  tested  under  a  pressure 
of  40  Ib.  per  sq.  in.,  but  it  is  wise  to  use  a  compressed-air 
pressure  of  not  more  than  10  Ib.  per  sq.  in.  A  pressure  of 
10  Ib.  per  sq.  in.  will  balance  an  oil  column  approxi- 
mately 24  ft.  high,  and  it  is  doubtful  whether  the  storage 
tank  will  ever  exceed  this  height  above  the  bottom  of 
the  tank  car.  The  use  of  air  pressure  in  this  way  is 
strongly  condemned  by  some  of  the  tank-car  lines,  and 
placards  are  attached  to  their  cars  warning  users  not  to 
employ  this  method  of  emptying  the  cars. 

Of  course,  compressed  air  is  not  available  in  a  great 
many  plants,  as  most  of  them  use  steam  to  atomize  the 
oil.  Steam  pressure  would  force  the  oil  out  of  the  tank 
car  just  as  well  as  air  pressure,  but  the  steam  would  con- 
dense, and  the  water  would  settle  to  the  bottom  of  the 
car  and  be  forced  out  with  the  oil  into  the  storage  tank. 
As  a  result,  steam  is  not  used  in  this  way. 

While  the  storage  tank  is  being  filled  with  oil,  the  air 
originally  contained  in  it  is  being  displaced  and  driven  out. 
To  afford  a  means  of  escape  for  this  air,  a  vent  pipe  is 
attached  to  one  of  the  flanges  at  the  top  of  the  tank. 
This  pipe  serves  another  purpose,  also,  in  that  it  allows 
the  escape  of  gases  rising  from  the  oil.  At  the  ordinary 
temperatures  at  which  the  oil  is  kept  in  the  storage 
tanks,  there  is  a  certain  amount  of  evaporation,  the 
lighter  and  more  volatile  constituents  changing  to  the 
gaseous  form.  The  vent  pipe,  open  to  the  outer  air, 
affords  easy  escape  for  these  gases  and  prevents  the  rise 
of  pressure  that  would  result  if  there  were  no  outlet. 


STORAGE  OF  OIL  FUEL  95 

One  of  the  simplest  forms  of  vent  pipe  is  shown  in  Fig. 
57.  It  consists  of  a  straight  piece  of  pipe  a  about  3  ft. 
long,  screwed  into  the  flange  b  on  top  of  the  tank  c. 
On  its  upper  end  a  return  bend  d  is  screwed,  and  over  the 
opening  e,  which  faces  downward,  a  piece  of  wire  gauze  / 
is  firmly  bound.  The  downward  curve  of  the  return 
bend  prevents  any  sparks  from  dropping  into  the  vent 
pipe  and  igniting  the  gases  arising  from  the  oil,  and  the 
gauze  prevents  the  flame  from  traveling  back  into  the 
tank  even  if  the  gases  are  ignited  at  the  opening  e,  outside 
the  gauze. 

Another  form  of  vent  pipe  is  shown  in  Fig.  58.  It  is  a 
straight  pipe  a,  somewhat  longer  than  the  diameter  of  the 
storage  tank  b,  and  is  screwed  into  a  flange  at  the  top  of 
the  tank.  At  the  top  of  the  pipe  is  a  cap  c  that  has  a 
number  of  openings  in  its  under  side.  These  openings 
allow  the  escape  of  air  or  gases  from  the  tank  and  are 
covered  with  wire  gauze  to  prevent  a  flare-back. 

This  particular  form  of  vent  pipe  serves  also  as  a  tell- 
tale, that  is,  as  an  indicator  to  show  the  amount  of  oil  in  t 
the  tank  at  any  specified  time.  Inside  the  cap  c  is  a 
small  pulley  over  which  a  wire  passes.  To  one  end  of  the 
wire  is  attached  a  float  d,  which  falls  or  rises  as  the  level 
of  the  oil  in  the  tank  changes.  To  the  other  end  of  the 
wire  is  attached  a  pointer  £,  and  as  the  float  falls  or  rises 
the  pointer  rises  or  falls  an  equal  distance.  On  the  vent 
pipe,  just  behind  the  pointer,  a  scale  is  marked,  divided 
into  feet  and  inches,  the  total  length  of  the  scale  being 
equal  to  the  inside  diameter  of  the  tank.  The  position 
of  the  pointer  then  indicates  the  depth  of  oil  in  the  tank, 
in  feet  and  inches.  A  table  may  easily  be  compiled  show- 


96 


OIL  FUEL  FOR  STEAM  BOILERS 


ing  the  amount  of  oil  in  the  tank  at  each  inch  of  depth. 
Then,  when  the  depth  of  oil  is  noted  on  the  telltale,  the 
amount  of  oil  corresponding  to  that  depth  can  quickly  be 
found. 

If  compressed  air  is  used  as  the  atomizing  agent  in  the 
plant,  or  is  otherwise  available,  the  form  of  indicator 
illustrated  in  Fig.  59  may  be  used.  A  glass  tube  a  of 


\ 

. 

Jc 

i 

1 

FIG.  59. — Indicator  for  oil- storage  tank. 

U, shape  is  fastened  to  a  board  b  that  in  turn  is  fastened 
to  the  wall  or  to  some  other  convenient  support.  The 
tube  is  partly  filled  with  mercury  and  the  leg  c  is  left 
open  to  the  air.  The  other  leg  d  is  connected  by  a  rubber 
tube  to  a  pipe  e  that  is  screwed  into  the  T-fitting  /. 
Two  other  pipes  are  connected  to  the  T.  That  at  g 
leads  to  the  compressed-air  system  and  is  fitted  with  a 
valve  h.  The  other  pipe  I  leads  to  the  bottom  of  the  oil- 


STORAGE  OF  OIL  FUEL  97 

storage  tank  j.  All  of  this  piping  may  be  of  i/8-in. 
wrought-iron  pipe. 

The  action  of  the  indicator  is  simple.  The  valve  h  is 
opened  very  slightly,  so  that  air  leaks  past  it  into  the  leg 
d  of  the  U-tube  and  into  the  pipe  i.  As  the  air  continues 
to  flow  into  the  pipe  i,  the  pressure  therein  grows  greater, 
and  this  pressure  acts  on  the  mercury  and  on  the  oil  with 
equal  intensity.  The  result  is  that  the  oil  in  the  pipe  k 
is  forced  down  until  finally  it  is  all  driven  out  at  the  lower 
end,  and  air  escapes  into  the  tank.  At  the  same  time  the 
increasing  pressure  of  the  air  forces  the  mercury  down 
in  the  leg  d  of  the  tube  and  up  in  the  leg  c.  Behind  the 
leg  d  is  a  graduated  scale  /,  and  the  position  of  the  top  of 
the  mercury  column  in  the  leg  d  is  read  on  the  scale. 

The  deeper  the  oil  in  the  storage  tank,  the  greater  is  the 
pressure  required  to  force  the  oil  down  out  of  the  pipe  k, 
and  consequently  the  lower  will  the  mercury  be  forced  in 
the  leg  d.  Every  reading  of  the  mercury  level  on  the 
scale  I  therefore  corresponds  to  a  certain  depth  of  oil  in 
the  storage  tank,  and  hence  to  a  certain  definite  quantity 
of  oil.  A  table  is  compiled  showing  the  amount  of  oil  in 
the  tank  corresponding  to  each  division  on  the  scale. 
By  comparing  the  reading  at  any  time  with  the  table  the 
corresponding  quantity  of  oil  can  be  found.  The  ac- 
curacy of  this  device  is  based  on  the  assumption  that 
practically  the  same  grade  of  oil  is  used  continuously. 
If  the  oil  varies  in  specific  gravity  from  time  to  time,  the 
scale  will  not  correctly  indicate  the  amount  of  oil  in  the 
tank. 

With  proper  care  there  is  little  danger  that  the  oil  in 
the  storage  tank  will  catch  fire;  however,  in  some  installa- 

7 


98  OIL  FUEL  FOR  STEAM  BOILERS 

tions  a  steam  pipe  is  connected  to  the  top  of  the  storage 
tank,  so  that  live  steam  may  be  run  direct  from  the  boiler 
into  the  tank  to  smother  any  fire  that  may  start. 

Reference  has  been  made  to  tables  from  which  the 
quantity  of  oil  on  hand  can  be  determined  when  the 
depth  of  oil  in  the  tank  is  known.  Two  such  tables  are 
given  herewith.  Table  III  shows  the  amount  of  oil  at 
each  inch  of  depth  in  a  cylindrical  tank  8  ft.  in  diameter 
and  28  ft.  long,  lying  in  a  horizontal  position.  Table 
IV  shows  the  amount  of  oil  at  each  inch  of  depth  in  a 
similar  tank  9  ft.  in  diameter  and  33  ft.  long,  placed  in 
the  same  position.  The  values  representing  the  amounts 
of  oil  are  given  in  United  States  gallons  and  are  only  ap- 
proximate, being  calculated  to  the  nearest  5  gal.;  how- 
ever, the  device  used  to  indicate  the  depth  of  oil  is  likely 
to  introduce  slight  errors,  so  that  these  values  are  suffi- 
ciently accurate  for  all  practical  purposes. 

The  method  of  using  the  tables  is  easy  to  understand. 
In  the  first  column  are  given  the  depths  of  oil  in  inches, 
or  fractions  of  a  foot,  and  at  the  heads  of  the  remaining 
columns  are  placed  the  depths  in  feet,  ranging  from  zero 
to  a  value  that  is  i  ft.  less  than  the  full  diameter  of 
the  tank.  To  find  the  amount  of  oil  corresponding  to 
a  given  depth  of  oil  in  the  tank,  the  column  headed  by 
the  number  of  feet  of  depth  is  first  located.  Then,  in 
the  first  column,  the  number  denoting  the  depth  in 
inches  is  located.  The  number  that  lies  on  the  same 
horizontal  line  with  this  depth  in  inches,  and  in  the 
column  headed  by  the  depth  in  feet,  is  the  quantity  of 
oil  in  gallons. 

Suppose  that  it  is  desired  to  find  the  amount  of  oil 


STORAGE  OF  OIL  FUEL  99 

in  a  tank  8  ft.  in  diameter  and  28  ft.  long  when  the  indi- 
cator shows  a  depth  of  3  ft.  8  in.  In  Table  III  the  col- 
umn headed  3  is  located,  and  in  this  column,  on  the  same 
line  with  8  in  the  first  column,  is  the  value  4,705;  there- 
fore, the  amount  of  oil  at  this  depth  is  4,705  gal. 

Again,  suppose  that  the  depth  of  oil  in  the  same  tank 
is  exactly  6  ft.,  that  is,  6  ft.  o  in.,  and  the  quantity  of  oil 
is  to  be  found.  There  is  no  zero  in  the  first  column  to 
represent  o  in.;  but  6  ft.  is  the  same  as  5  ft.  12  in.  Then, 
the  quantity  of  oil  at  a  depth  of  5  ft.  12  in.,  or  6  ft.,  is 
found  in  the  column  headed  5,  on  the  same  line  with  12, 
and  is  8,470  gal.  In  the  same  way,  the  amount  of  oil  at 
a  depth  of  4  ft.,  or  3  ft.  12  in.,  is  5,265  gal.,  and  at  a 
depth  of  8  ft.,  or  7  ft.  12  in.,  the  tank  is  full  and  con- 
tains 10,530  gal. 

If  the  depth  of  oil  is  not  more  than  i  ft.,  or  12  in.,  the 
quantity  is  found  in  the  second  column,  headed  o.  For 
instance,  if  the  depth  of  oil  is  9  in.,  which  is  o  ft.  9  in., 
the  amount  is  500  gal.,  because  500  is  in  the  column 
headed  o  and  on  the  same  line  as  9  in  the  first  column. 
The  values  for  the  larger  size  of  tank  are  found  from 
Table  IV  by  the  same  methods  as  those  described  in 
connection  with  Table  III. 


100 


OIL  FUEL  FOR  STEAM  BOILERS 


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CHAPTER  X 

COMBUSTION  OF  OIL  FUEL 

The  efficiency  of  combustion  of  oil  fuel  is  dependent 
on  the  furnace  in  which  the  burning  takes  place.  The 
burner  should  give  a  finely  atomized  spray  of  oil,  but  the 
furnace  must  be  of  such  size  and  shape  as  to  enable 
the  oil  to  be  vaporized,  mixed  with  the  required  quantity 
of  air  and  burned  to  carbon  dioxide  before  the  resulting 
products  of  combustion  are  allowed  to  come  in  contact 
with  the  boiler  surfaces. 

The  effect  of  too  small  a  furnace  is  to  cause  incomplete 
combustion.  The  oil  is  sprayed  into  the  furnace  in  the 
form  of  minute  globules,  each  of  which  must  be  converted 
into  vapor  before  it  can  burn.  The  heat  required  for 
this  vaporization  is  derived  from  the  highly  heated 
firebrick  with  which  the  furnace  is  lined.  Each  globule 
of  oil,  on  being  converted  into  vapor,  expands  to  many 
times  its  original  volume,  and  this  sudden  increase  of 
the  volume  of  the  oil  makes  it  necessary  to  have  a  furnace 
that  will  accommodate  the  expansion.  When  the 
furnace  is  too  small  the  expansion  at  the  moment  of 
vaporization  increases  the  volume  so  greatly  that  the 
gases  must  travel  very  rapidly,  and  the  result  is  that 
they  pass  out  and  come  in  contact  with  the  boiler 
tubes  or  surfaces  before  the  air  has  been  thoroughly 
mixed  with  them  and  before  combustion  is  complete. 

102 


COMBUSTION  OF  OIL  FUEL  103 

The  burner  also  affects  the  furnace  efficiency;  for  the 
greater  the  size  of  the  oil  globules  the  longer  will  be  the 
time  required  to  convert  them  into  vapor.  Their  ex- 
pansion produces  a  pressure  in  the  furnace,  and  this 
pressure,  aided  by  the  steam  blast,  quickly  drives  them 
on  into  the  boiler  passages.  As  a  result,  only  the 
smallest  globules  are  vaporized  and  burned  in  the  furnace 
and  the  others  are  carried  into  the  boiler  passages,  where 
their  temperature  is  lowered  and  they  are  only  partly 
burned.  Even  the  carbon  dioxide  formed  by  combustion 
in  the  furnace  may  be  converted  to  monoxide  by  taking 
up  carbon  from  the  unburned  gases  beyond  the  furnace. 

If  there  is  a  very  large  percentage  of  carbon  monoxide 
in  the  gases,  secondary  combustion  may  occur;  that 
is,  the  monoxide  may  burn  on  its  way  through  the 
passages  of  the  boiler,  or  even  in  the  uptake  or  the 
chimney.  Although  some  heat  may  thus  be  recovered, 
the  combustion  takes  place  under  poor  conditions  and  is 
not  nearly  so  efficient  as  when  it  takes  place  in  the 
furnace.  So,  whether  secondary  combustion  occurs  or 
not,  heat  is  lost. 

The  final  effect  of  too  small  a  furnace,  therefore,  is 
to  give  too  rapid  a  travel  of  the  gases  through  the  fur- 
nace, with  the  subsequent  formation  of  carbon  mon- 
oxide and  waste  of  heat.  For  these  reasons  the  oil 
should  be  broken  up  into  a  spray  almost  too  fine  to  be 
seen,  and  the  furnace  should  have  sufficient  volume  to 
allow  combustion  to  be  completed  before  the  gases 
leave  it.  In  this  way  the  maximum  temperature  will  be 
obtained  and  the  loss  due  to  carbon  monoxide  will  be 
obviated. 


104  OIL  FUEL  FOR  STEAM  BOILERS 

The  amount  of  air  required  for  the  complete  combus- 
tion of  a  pound  of  oil  fuel  of  known  composition  may 
be  calculated  approximately  by  the  formula 

W  =  ii.6C  +  34.8# 
in  which 

W  =  pounds  of  air  per  pound  of  oil; 
C  =  percentage  of  carbon,  expressed  decimally; 
H  =  percentage  of  hydrogen,  expressed  decimally. 

For  example,  suppose  that  a  certain  grade  of  crude 
oil  is  found  to  contain  85  per  cent,  of  carbon  and  12  per 
cent,  of  hydrogen.  The  least  amount  of  air  that  will 
burn  a  pound  of  this  oil  completely  is 

W  =  n. 6  X  0.85  +  34.8  X  0.12  =  14  lb.,  very  nearly. 

Slight  differences  in  the  relative  amounts  of  carbon 
and  hydrogen  in  oils,  together  with  the  presence  of 
such  elements  as  oxygen,  nitrogen  and  sulphur  will 
cause  the  minimum  amount  of  air  per  pound  of  oil  to 
be  greater  or  less  than  that  just  calculated;  but  with 
the  oils  ordinarily  used  as  fuels  in  steam-boiler  work, 
from  13  lb.  to  14  lb.  of  air  would  be  required  per  pound 
of  oil  if  the  combustion  were  ideal  and  complete. 

Just  as  in  the  combustion  of  coal,  so  in  the  combus- 
tion of  oil  fuel  it  is  necessary  to  admit  an  excess  of  air 
to  the  furnace.  The  reason  is  the  same,  namely,  to  in- 
sure a  sufficient  supply  of  oxygen  to  enable  each  particle 
of  combustible  matter  to  be  burned  completely.  But 
there  is  a  great  difference  between  the  excess  required 
for  solid  fuel  and  that  required  for  liquid  fuel.  The 
average  coal-burning  furnace  seldom  uses  less  than  one 
and  one-half  times  the  minimum  atnount  of  air  re- 


COMBUSTION  OF  OIL  FUEL  105 

quired  for  complete  combustion,  and  usually  it  requires 
twice  the  amount  or  even  more;  that  is,  the  excess  of 
air  ordinarily  ranges  from  50  per  cent,  to  100  per  cent, 
and  frequently  exceeds  the  latter  value.  With  oil  fuel, 
the  excess  of  air  may  be  kept  as  low  as  10  per  cent,  by 
efficient  furnace  arrangement  and  careful  regulation,  and 
it  is  not  uncommon  to  find  oil-burning  plants  in  which 
the  excess  of  air  is  not  over  20  per  cent. 

The  reason  for  the  smaller  supply  of  air  required 
lies  in  the  fact  that  the  conditions  in  the  oil-burning 
furnace  are  much  more  favorable  to  the  thorough  mix- 
ing of  the  air  and  the  fuel  than  is  the  case  in  a  coal- 
burning  furnace.  The  oil  is  sprayed,  and  the  air  is  ad- 
mitted in  such  a  way  as  to  mingle  intimately  and  uni- 
formly with  it.  In, the  case  of  coal  the  air  must  pass 
up  through  the  fuel  bed,  which  is  of  varying  thickness, 
with  the  result  that  the  resistance  is  highest  and  the 
flow 'least  where  the  supply  should  be  greatest,  that  is, 
at  the  thickest  part  of  the  bed.  The  use  of  a  small 
excess  of  air  conduces  to  greater  boiler  efficiency  be- 
cause it  results  in  a  higher  temperature  of  the  products 
of  combustion.  For  the  heat  generated  is  contained  in 
a  much  smaller  weight  of  gases  than  in  the  case  of  a 
coal  fire. 

The  formation  of  soot  or  smoke  is  due  to  the  pres- 
ence of  unburned  carbon  in  the  gases,  and  it  may  occur 
even  when  a  sufficient  amount  of  air.  is  being  admitted 
to  the  furnace.  The  point  to  be  observed  is  that  the 
combustible  matter  shall  not  only  be  surrounded  with 
an  ample  supply  of  oxygen,  but  that  the  temperature  of 
ignition  shall  be  maintained  until  combustion  is  com- 


106  OIL  FUEL  FOR  STEAM  BOILERS 

plete.  In  the  case  of  oil  fuel  the  spray  is  first  con- 
verted into  gaseous  hydrocarbons,  and  these  hydrocar- 
bons are  broken  up  into  free  hydrogen  and  free  carbon. 
If  there  is  enough  oxygen  present  and  the  temperature 
is  sufficiently  high,  the  hydrogen  will  burn  to  steam 
and  the  carbon  to  carbon  dioxide;  but  if  the  tempera- 
ture of  the  mixed  gases  is  lowered  by  admitting  an 
excessive  amount  of  cold  air,  or  by  allowing  the  gases 
to  impinge  on  cold  boiler  surfaces,  combustion  will  be 
prevented  and  the  unburned  combustible  will  be  carried 
along  with  the  gases  and  go  to  waste. 

The  free  unburned  carbon  is  in  the  form  of  fine  par- 
ticles that,  on  cooling,  assume  the  characteristic  black 
color  and  appear  as  smoke  or  collect  as  soot  on  the 
boiler  surfaces.  This  explains  the  use  of  firebrick  lin- 
ings and  baffles  in  furnaces  and  combustion  chambers 
in  which  oil  is  burned.  The  brickwork  becomes  in- 
candescent and  maintains  the  temperature  necessary 
to  insure  the  union  of  the  carbon  and  the  oxygen. 

Although  the  condition  of  the  fire  in  an  oil-burning 
furnace  can  be  judged  by  observing  the  flame  and 
noting  the  roaring  sound  made  by  the  burners,  it  is  well 
if  the  fireman  can  keep  an  eye  on  the  gases  issuing 
from  the  top  of  the  chimney.  The  smoke,  if  there  is 
any,  should  be  very  light  and  uniform  in  color.  If  it 
becomes  dense,  it  is  a  sign  that  the  burners  need  to  be 
regulated  or  the  air  supply  readjusted. 

Absence  of  smoke  is  not  necessarily  a  sign  of  per- 
fect combustion,  and  no  fireman  should  assume  that  he 
is  obtaining  the  best  results  in  the  furnace  merely  be- 
cause there  is  no  smoke  issuing  from  the  chimney;  for 


COMBUSTION  OF  OIL  FUEL  107 

the  supply  of  air  may  be  greatly  in  excess  of  that  re- 
quired for  economy.  On  this  account  it  is  wise  to 
analyze  the  flue  gases,  or  to  install  a  continuous  CO2 
recorder,  so  that  the  efficiency  of  combustion  may  be 
under  the  observation  of  the  management.  Particularly 
is  this  true  of  the  plant  that  has  been  altered  from  the 
burning  of  coal  to  the  burning  of  oil;  for  it  is  found 
that  a  fireman  accustomed  to  fire  coal  is  very  apt  to 
admit  entirely  too  much  air  when  he  takes  up  the  man- 
agement of  oil  burners. 

The  idea  that  the  admission  of  steam  to  the  furnace 
increases  the  amount  of  heat  generated  is  an  error  that 
is  apparently  based  on  a  misunderstanding  of  the  action 
of  the  steam  during  combustion.  The  steam  that  enters 
with  the  oil  is  heated  to  the  temperature  of  the  furnace, 
which  is  so  high  that  the  steam  is  decomposed,  or 
broken  up,  into  the  elements  hydrogen  and  oxygen. 
In  the  presence  of  the  carbon  and  oxygen  in  the  gases, 
however,  the  hydrogen  and  oxygen  thus  liberated 
are  taken  into  combination  again,  forming  steam  and 
carbon  dioxide.  Moreover,  the  amount  of  heat  result- 
ing from  the  burning  of  the  hydrogen  is  precisely  equal 
to  the  amount  that  was  required  to  set  that  hydrogen  free 
during  the  decomposition  of  the  steam.  This  is  directly 
in  compliance  with  the  law  of  conservation  of  energy. 
The  net  gain,  therefore,  is  nothing,  and  the  final  result 
is  the  same  as  though  the  steam  had  passed  through  the 
furnace  without  being  decomposed.  In  other  words, 
the  steam  not  only  does  not  add  to  the  heat  generated 
but  actually  carries  away  a  part  of  the  heat  because  it 
escapes  to  the  chimney  in  a  highly  superheated  condition. 


CHAPTER  XI 

MANAGEMENT  OF  OIL-BURNING  PLANTS 

The  management  of  an  oil-burning  plant  differs  very 
considerably  from  the  management  of  a  coal-burning 
plant  because  of  the  rapidity  with  which  any  alteration 
in  the  rate  of  firing  affects  the  generation  of  steam. 
With  a  coal  fire  the  response  to  an  increased  rate  of  fir- 
ing is  slow,  because  it  is  necessary  for  the  fresh  fuel 
to  become  heated  to  the  temperature  of  ignition  before 
it  can  burn  and  give  off  heat.  In  the  case  of  an  oil  fire, 
however,  the  combustion  keeps  pace  with  the  rate  of 
feeding  the  oil,  so  that  an  increased  flow  of  oil  is  im- 
mediately followed  by  an  increased  generation  of  heat. 

The  fact  that  an  oil-burning  plant  is  so  quickly  re- 
sponsive to  alterations  in  the  conditions  of  combustion 
makes  it  necessary  to  observe  care  in  the  regulation  of 
the  burners  and  the  control  of  the  air  supply.  It  is  par- 
ticularly necessary  to  guard  against  the  admission  of 
too  much  air,  which  will  dilute  the  products  of  combus- 
tion and  cause  loss  of  heat.  A  fireman  accustomed  to 
the  use  of  solid  fuel  may  find  it  difficult  to  learn  to  re- 
duce the  air  supply  sufficiently  for  the  economic  burn- 
ing of  oil,  as  oil  requires  a  much  smaller  excess  of  air. 

The  method  to  be  used  in  starting  an  oil  fire  under 
a  boiler  will  depend  on  whether  the  boiler  is  the  only 
one  in  the  plant  or  whether  there  are  other  boilers 
already  under  steam.  If  steam  is  not  available  from 

108 


MANAGEMENT  OF  OIL-BURNING  PLANTS       109 

some  auxiliary  source,  it  is  necessary  to  start  an  ordi- 
nary wood  fire  and  get  up  steam  pressure  enough  to 
atomize  the  oil.  If  the  boiler  is  one  that  has  been  con- 
verted from  coal  burning  to  oil  burning,  and  the  grates 
are  still  in  place,  covered  with  firebrick,  the  wood  fire 
is  built  right  on  the  firebrick  layer  and  is  kept  going 
until  the  steam  gage  on  the  boiler  shows  a  pressure  of 
at  least  20  lb.,  which  will  be  sufficient  to  atomize  the  oil 
for  starting  the  fire.  It  is  not  necessary  to  remove  the 
burner  while  this  fire  is  under  way,  but  the  fire  should 
be  kept  at  a  safe  distance  from  the  burner,  so  that  the 
heat  will  not  warp  the  tip  or  injure  the  pipes. 

When  the  steam  pressure  reaches  20  lb.  the  oil-pres- 
sure pump  should  be  started  and  the  steam  valve  on  the 
burner  should  be  opened.  Steam  should  be  allowed  to 
blow  through  the  burner  until  the  issuing  jet  appears 
to  be  dry.  Then  the  oil  valve  is  opened  and  oil  is 
allowed  to  flow  into  the  burner.  The  spray  of  oil  will 
be  directed  into  the  wood  fire  on  the  floor  of  the  fur- 
nace and  will  be  ignited,  after  which  the  burner  will 
continue  its  operation  in  the  usual  way.  The  wood  fire 
may  be  allowed  to  burn  out  or  it  may  be  raked  out  after 
the  oil  fire  has  been  started. 

If  there  are  other  boilers  in  use,  so  that  a  supply  of 
steam  is  at  hand,  the  operation  of  starting  an  oil  fire 
under  a  cold  boiler  is  made  much  simpler  and  shorter. 
The  first  thing  to  do  is  to  open  the-  damper  to  its  full 
extent.  The  steam  and  oil  stop  valves  are  kept  closed, 
but  the  needle  valve  or  oil-regulating  valve  is  opened 
slightly.  Now  steam  is  admitted  to  the  burner  and  is 
allowed  to  flow  until  the  pipes  and  the  burner  are 


110  OIL  FUEL  FOR  STEAM  BOILERS 

heated  and  the  issuing  current  seems  to  be  dry,  which 
indicates  that  there  is  no  condensation  collected  in  the 
steam-supply  system.  Next,  a  bunch  of  waste  saturated 
with  oil  should  be  lighted  and  placed  inside  the  fur- 
nace, on  the  firebrick,  directly  in  the  path  of  the  steam 
blast.  Then  the  fire-door  should  be  closed  quickly  and 
the  oil  valve  should  be  opened.  The  oil  will  flow  through 
the  partly  opened  needle  valve  or  oil-regulating  valve 
and  the  spray  will  be  ignited  by  the  burning  waste. 
After  the  fire  is  thus  started,  the  combustion  may  be 
regulated  by  adjusting  the  flow  of  oil  and  steam  and  by 
changing  the  air  supply  through  manipulation  of  the 
ashpit  doors  and  the  damper. 

Before  starting  the  fire,  it  is  a  wise  precaution  to 
blow  steam  through  the  oil  side  of  the  burner  to  make 
sure  that  the  oil  passages  are  clear.  This  is  done  by 
opening  the  by-pass  valve  and  the  steam  valve.  After 
the  fire  is  started  the  intensity  of  the  fire  should  not  be 
increased  too  rapidly,  as  there  is  danger  in  forcing  the 
fires  under  a  cold  boiler. 

The  condition  of  the  fire  is  observed  through  peep- 
holes that  are  placed  in  front  of  the  setting  or  at  the 
sides.  When  the  boiler  and  its  setting  have  become 
heated  to  the  usual  working  temperature  the  interior 
of  the  furnace  should  appear  to  be  filled  with  flame,  the 
color  of  which  should  verge  on  a  dazzling  white.  The 
flame  should  be  steady  and  not  surging  or  gusty.  An 
experienced  fireman  can  judge  the  condition  of  his  fire 
very  accurately  by  observing  the  color  of  the  flame,  but 
it  is  advantageous  if  he  can  also  see  the  top  of  the 
chimney. 


MANAGEMENT  OF  OIL-BURNING  PLANTS       111 

The  combustion  of  oil  is  accompanied  by  a  roaring 
noise,  and  the  nature  of  this  roaring  also  serves  as  a 
guide  to  the  conditions  existing  in  the  furnace.  It  is 
noticeable  that  an  excessive  supply  of  cold  air  greatly 
increases  the  noise,  and  that  preheating  of  the  air  sup- 
ply renders  the  combustion  much  quieter.  It  is  natural 
to  suppose,  therefore,  that  the  reduction  of  roaring  in 
the  furnace  is  accompanied  by  an  increased  efficiency 
of  combustion,  since  it  is  obtained  by  cutting  down  the 
excess  of  air  and  by  increasing  its  temperature. 

The  formation  of  smoke  may  be  traced  to  an  insuffi- 
cient supply  of  air,  an  oversupply  of  oil  or  too  little 
steam  to  atomize  the  oil  thoroughly.  A  burner  that  has 
not  been  properly  cleaned  and  that  is  clogged  or  im- 
perfectly adjusted  will  produce  an  unsteady  flame  and 
may  cause  smoke.  If  there  are  scintillating  particles  in 
the  flame  and  they  appear  to  fall  to  the  floor  of  the  fur- 
nace, it  may  be  concluded  that  the  atomization  is  im- 
perfect. The  pressure  of  the  atomizing  agent  should 
therefore  be  increased.  If  there  is  water  in  the  oil  or 
in  the  steam,  the  burner  will  spit  and  act  erratically. 
A  similar  sputtering  may  be  caused  by  the  presence  of 
gases  in  the  oil,  due  to  an  excessive  heating  of  the  oil  on 
its  way  to  the  burner. 

In  the  average  small  plant  using  liquid  fuel  the  burn- 
ers are  regulated  by  hand  to  accommodate  the  rate  of 
firing  to  the  demand  for  steam.  This  can  be  done  read- 
ily because  the  number  of  burners  to  be  adjusted  is 
not  great;  but  in  a  very  large  plant  this  method  of  con- 
trol would  be  irksome,  particularly  if  the  load  were  sub- 
ject to  wide  and  frequent  changes.  With  hand  regula- 


112  OIL  FUEL  FOR  STEAM  BOILERS 

tion  of  the  separate  burners  the  economy  depends  on 
the  intelligence  of  the  fireman  in  judging  the  conditions 
of  combustion  and  in  the  quickness  with  which  he  ad- 
justs the  burners  to  changes  of  load. 

Automatic  regulation  is  employed  in  some  of  the 
larger  plants.  The  means  by  which  regulation  is  ef- 
fected varies,  but  the  end  attained  is  the  same,  namely, 
an  increase  or  decrease  in  the  rate  of  firing  to  correspond 
to  an  increase  or  decrease  of  load.  An  increased  de- 
mand for  steam  is  evidenced  by  a  decrease  of  steam 
pressure  in  a  boiler.  One  system  of  automatic  control 
therefore  uses  a  regulating  valve  on  the  oil  line  to  the 
burners.  This  valve  determines  the  rate  of  flow  of 
the  oil,  and  its  stem  is  attached  to  a  spring  and  to  a 
diaphragm  that  is  acted  on  by  the  steam  pressure. 
The  pressure  of  the  spring  and  the  steam  pressure  act 
to  oppose  each  other,  and  the  tension  of  the  spring  can 
be  altered  to  suit  conditions.  By  setting  this  spring  to 
the  proper  tension,  any  decrease  of  steam  pressure  fol- 
lowing an  increased  load  on  the  boiler  will  allow  the 
spring  to  open  the  valve  slightly  and  more  oil  will  be 
admitted  to  the  burners.  In  this  way  the  rate  of  com- 
bustion can  be  made  to  follow  the  demand  for  steam 
very  closely.  In  this  system  the  pressure  of  the  oil  as 
supplied  by  the  pump  remains  constant. 

In  another  system  of  automatic  regulation  the  regu- 
lating valve  takes  the  form  of  a  pump  governor.  When 
an  increase  of  load  comes  on,  the  governor  admits  more 
steam  to  the  pump,  which  increases  its  speed  and  gives 
a  higher  oil  pressure.  The  oil  valves  at  the  burners  are 
left  open,  and  the  result  of  the  higher  pressure  is  an 


MANAGEMENT  OF  OIL-BURNING  PLANTS       113 

increased  flow  of  oil.  There  is  a  greater  amount  of  heat 
thus  generated  and  the  steam  pressure  is  quickly  brought 
back  to  normal  by  the  accelerated  evaporation.  While 
the  steam  pressure  is  increasing  the  governor  is  gradually 
cutting  down  the  speed  of  the  pump.  In  this  way  the 
steam  pressure  is  kept  fairly  uniform. 

Of  course,  an  increased  flow  of  oil  demands  an  in- 
creased flow  of  steam  to  atomize  it  properly.  In  the 
system  of  control  just  described  the  steam  supply  is 
regulated  by  a  valve  whose  stem  is  fastened  to  a  dia- 
phragm acted  on  by  the  oil  pressure.  An  increased  oil 
pressure  immediately  causes  an  increased  opening  of 
the  steam  valve,  and  thus  the  correct  ratio  of  steam  to 
oil  is  maintained. 

The  draft  required  for  the  burning  of  oil  fuel  is  very 
small,  ranging  from  about  1/8  in.  to  1/2  in.  of  water. 
This  is  much  less  than  is  required  for  the  burning  of 
solid  fuels  and  is  accounted  for  by  the  fact  that  in  an 
oil-burning  boiler  the  only  resistance  to  be  overcome  by 
the  draft  is  that  due  to  the  friction  of  the  gases  in  pass- 
ing through  the  furnace,  among  or  through  the  tubes 
and  along  the  breeching  and  the  chimney  to  the  outer 
air.  In  a  coal-burning  boiler  the  draft  must  not  only 
overcome  these  resistances  but  must  also  cause  the  air 
supply  to  rise  through  the  bed  of  fuel  on  the  grates. 
For  this  reason  the  chimney  of  a  coal-burning  plant 
will  give  too  strong  a  draft  when  the  fuel  is  changed 
to  oil,  and  to  prevent  the  inrush  of  too  much  air  the 
damper  must  be  closed  to  a  greater  extent  than  when 
solid  fuel  is  used. 

The  regulation  of  the  air  supply  to  the  furnace  may 

8 


114  OIL  FUEL  FOR  STEAM  BOILERS 

be  effected  either  by  means  of  the  damper  alone  or  by 
means  of  the  damper  and  the  ashpit  doors.  When  the 
damper  alone  is  used,  the  ashpit  doors  are  left  wide 
open  and  the  rate  at  which  air  flows  into  the  furnace  is 
controlled  by  the  amount  of  opening  of  the  damper. 
The  advantage  of  this  system  of  control  is  that  at  all 
times  there  is  ample  opening  for  the  admission  of  air 
and  the  air  enters  at  a  rate  sufficient  to  replace  the 
gases  that  escape  to  the  chimney.  By  impeding  the 
escape  of  hot  gases  at  the  damper  the  hot  products  of 
combustion  are  kept  in  contact  with  the  boiler  surfaces 
for  a  longer  period  and  the  rate  of  travel  is  reduced, 
thus  giving  ample  time  for  complete  combustion. 

It  is  probable,  however,  that  in  the  larger  number 
of  plants  the  regulation  is  accomplished  by  both  the 
damper  and  the  ashpit  doors.  When  the  load  on  the 
boiler  decreases  the  amounts  of  air  and  oil  are  reduced. 
This  results  in  a  corresponding  reduction  of  the  weight 
of  gases  formed  in  the  furnace,  and  so  the  damper 
should  be  moved  toward  its  closed  position.  When  the 
demand  for  steam  increases  the  opposite  adjustment 
must  be  made.  In  any  case,  the  object  to  be  attained  is 
efficient  combustion,  and  this  should  be  done  with  the 
least  possible  amount  of  air.  To  judge  as  to  when  this 
point  has  been  reached,  the  air  supply  may  be  cut  down 
until  smoke  is  formed,  indicating  that  there  is  too  little 
air.  Then  the  supply  may  be  increased  gradually  until 
the  smoke  disappears  and  only  a  slight  haze  is  visible 
at  the  top  of  the  chimney. 

When  an  oil-burning  boiler  is  to  be  shut  down,  the 
stop  valve  on  the  oil  line  to  the  burners  should  be 


MANAGEMENT  OF  OIL-BURNING  PLANTS      115 

closed  first  of  all,  thus  cutting  off  the  flow  of  oil  and 
stopping  combustion  in  the  furnace.  Next,  the  steam 
valve  should  be  closed  until  only  a  small  jet  of  steam 
escapes  from  the  burner.  The  oil  side  of  the  burner 
should  then  be  blown  out,  which  is  done  by  opening  the 
oil-regulating  valve  on  the  burner,  the  by-pass  valve  and 
then  the  steam  valve.  This  precaution  is  necessary  to 
prevent  clogging  of  the  burner;  for  if  the  oil  is  allowed 
to  remain  stagnant  in  the  burner  and  its  connecting 
pipes,  the  heat  of  the  setting  will  carbonize  the  oil  and 
bake  its  tarry  constituents  on  the  inside  of  the  passages, 
and  there  will  be  trouble  and  delay  when  the  burner  is 
again  put  into  service.  The  ashpit  doors  and  any  other 
openings  for  the  admission  of  cold  air  to  the  furnace 
should  be  closed  and  the  damper  opened,  so  that  the 
setting  may  not  cool  too  rapidly. 

As  a  usual  thing,  the  heat  stored  in  the  brick  lining 
of  the  furnace  will  reign ite  the  oil  spray  if  the  flow  of 
oil  is  interrupted  for  a  few  seconds.  If  the  supply  of  oil 
is  cut  off  for  some  time,  however,  the  temperature  of 
the  furnace  may  fall  to  such  a  point  that  the  oil  can- 
not be  ignited  by  the  heat  of  the  firebrick.  In  such  a 
case  the  fireman  should  shut  off  all  oil  and  then  close  the 
steam  valve,  putting  the  burners  out  of  action.  Then 
he  should  throw  a  bunch  of  burning  waste  into  the  fur- 
nace, close  the  fire-door  and  restart  the  burner  in  the 
usual  way. 

The  inflammable  nature  of. oil  fuel  renders  accidental 
fires  a  possibility.  Should  oil  escape  from  the  pipes 
and  become  ignited,  the  flames  should  be  smothered  by 
scattering  sand  or  earth  over  the  surface  of  the  blazing 


116  OIL  FUEL  FOR  STEAM  BOILERS 

liquid.  The  air  is  thus  shut  off  from  the  oil  and  com- 
bustion dies  out  because  of  the  lack  of  oxygen.  It  is 
useless  to  attempt  to  put  out  an  oil  fire  by  turning 
water  on  it,  because  the  only  effect  of  the  water  will  be 
to  spread  the  oil  without  extinguishing  the  flame. 


CHAPTER  XII 
PURCHASE  OF  OIL  FUEL 

When  it  comes  to  the  purchase  of  oil  fuel,  the  buyer 
is  interested  in  obtaining  the  greatest  possible  heat 
value  for  the  money  expended;  therefore,  he  wishes  to 
know  the  amounts  of  water,  sulphur  and  sediment  in  the 
oil,  the  heat  value,  the  flash  point  and  the  specific 
gravity.  From  a  knowledge  of  these  properties  he  can 
determine  how  well  the  oil  is  suited  to  his  purposes. 

The  Bureau  of  Mines  has  issued  a  pamphlet  detailing 
the  specifications  for  oil  purchased  by  the  United  States 
government  and  describing  methods  of  sampling.  The 
following  information  concerning  the  requirements  of 
oil  for  fuel  purposes  and  the  methods  of  obtaining 
samples  is  taken  largely  from  this  publication. 

The  oil  available  for  fuel  may  be  either  crude  oil  or 
fuel  oil.  In  the  first  case  it  is  simply  natural  petroleum 
as  it  comes  from  the  well,  and  in  the  latter  case  it  is 
the  residue  left  after  the  lighter  and  more  volatile  con- 
stituents of  crude  oil  have  been  driven  off.  In  either 
case  the  oil  should  be  homogeneous,  or  of  uniform  com- 
position throughout.  It  should  not  be  a  mixture  of 
light  and  heavy  oils  in  such  proportions  as  to  give  the 
desired  specific  gravity. 

If  it  is  a  fuel  oil — that  is,  has  been  subjected  to  a 
preliminary  heat  treatment — the  temperature  to  which 

117 


118  OIL  FUEL  FOR  STEAM  BOILERS 

it  was  heated  should  not  have  been  so  high  as  to  burn 
it,  nor  should  the  temperature  have  been  so  high  as  to 
cause  the  separation  of  carbon,  which  would  afterward 
appear  as  flecks  in  the  oil. 

To  be  quite  safe  the  oil  should  have  a  flash  point  of 
not  less  than  140  deg.  Fahr.,  and  this  point  should  be 
determined  by  means  of  a  closed  tester.  The  flash  point 
of  an  oil  is  the  temperature  at  which  the  oil  will  give  off 
vapors  that  will  ignite  when  a  naked  flame  is  brought 
in  contact  with  them.  A  crude  form  of  test  for  the 
flash  point  may  be  made  by  putting  a  sample  of  oil  in  a 
cup,  placing  the  cup  in  an  iron  vessel  containing  sand 
and  applying  heat  to  the  sand  so  as  to  increase  the  tem- 
perature of  the  oil  gradually.  At  short  intervals  during 
the  heating  the  flame  of  a  match  is  passed  over  the  sur- 
face of  the  oil  and  about  1/2  in.  from  it.  Eventually  a 
point  will  be  reached  when  the  gases  rising  from  the 
heated  oil  will  ignite  and  burn  with  a  blue  flash  when 
the  match  is  applied.  The  temperature  of  the  oil  when 
this  action  is  first  noticed  is  called  the  flash  point. 

The  open  cup,  though  forming  a  simple  means  of  find- 
ing the  flash  point,  is  not  accurate,  because  there  is 
too  much  opportunity  for  variation  in  the  conditions 
under  which  the  test  is  conducted.  It  is  very  difficult 
to  screen  an  open  cup  from  all  drafts  and  air  currents, 
and  if  these  are  not  prevented  the  gases  rising  from  the 
oil  will  be  diffused  more  or  less  quickly  and  the  results 
will  not  be  correct.  The  quantity  of  air  in  the  top  of 
the  cup,  just  above  the  surface  of  the  oil,  influences  the 
flash  point.  The  rate  at  which  the  oil  is  heated  will 
affect  the  result.  The  more  rapid  the  heating,  the  more 


PURCHASE  OF  OIL  FUEL  119 

rapid  the  formation  of  gases  and  the  lower  is  the  flash 
point. 

The  quantity  of  oil  also  has  a  bearing  on  the  result 
obtained.  The  greater  the  quantity  of  oil,  the  greater 
is  the  quantity  of  gases  driven  off  and  the  lower  the 
flash  point.  The  form  and  size  of  the  oil  cup  are  con- 
trolling factors.  The  evaporation  is  most  rapid  with 
a  large,  shallow  cup,  and  the  flash  point  with  such  a  cup 
is  lower.  The  most  nearly  uniform  results  are  to  be 
obtained  with  a  cup  that  is  fairly  deep  in  comparison 
with  its  diameter  and  that  is  filled  about  half  full. 

The  flame  by  which  the  test  is  applied  should  be  of 
constant  size  and  shape  if  uniform  results  are  desired, 
and  the  time  during  which  it  acts  should  always  be  the 
same.  Again,  its  distance  from  the  surface  of  the  oil 
at  the  instant  the  test  is  made  should  not  vary.  The 
larger  the  flame  or  the  closer  it  is  brought  to  the  sur- 
face of  the  oil,  the  lower  is  the  flash  point.  It  is  best 
to  pass  the  flame  across  the  center  of  the  cup,  from  one 
edge  to  the  other,  because  the  mixture  of  gas  and  air  is 
most  complete  at  the  edge  of  the  cup. 

To  obtain  accuracy  of  results  and  to  allow  the  results 
to  be  compared,  flash  tests  should  be  made  in  a  closed 
tester,  such  as  the  Abel  tester,  shown  in  section  in  Fig. 
60.  It  consists  of  a  cup  #,  about  2  in.  in  diameter  and 
2  1/4  in.  deep,  into  which  the  oil  to  be  tested  is  poured, 
always  to  the  same  level,  as  indicated  by  the  tip  of  a 
bent  wire  b  soldered  to  the  inside  of  the  cup.  The 
cover  of  the  cup  carries  a  thermometer  c  for  register- 
ing the  temperature  of  the  oil.  It  also  carries  a  slide  d 
to  which  is  swiveled  a  lamp  e  by  which  the  flash  test  is 


120 


OIL  FUEL  FOR  STEAM  BOILERS 


made.     The  arrangement  of  the  lamp  on  the  cover  of 
the  cup  is  clearly  shown  in  Fig.  61.     The  body  of  the 


FIG.  60. — Section  of  oil  tester. 

lamp  is  filled  with  colza  oil  or  rape  oil,  and  at  the  end 
of  the  spout  is  a  wick.  In  the  slide  is  a  rectangular 
slot,  and  under  the  slide  are  three  slots  in  the  cover  of 


PURCHASE  OF  OIL  FUEL  121 

the  cup;  thus,  when  the  slide  is  drawn  across  the  cover, 
its  slot  registers  with  the  slots  in  the  cover.  A  pin 
projects  from  the  slide,  and  when  the  latter  is  pulled 
out  the  pin  tilts  the  narrow  spout  of  the  lamp  down  into 
the  slot  and  thus  brings  the  flame  in  contact  with  the 
gases  in  the  cup.  There  is  a  white  bead/,  Fig.  60,  fixed 
to  the  cover  just  opposite  the  flame  of  the  test  lamp, 
and  the  size  of  this  bead  is  a  guide  to  the  size  of  the 
test  flame  to  be  used. 


FIG.  61. — Lamp  of  tester  for  flash  point  of  oil. 

The  oil  to  be  tested  is  heated  by  a  water  bath  con- 
tained in  the  copper  vessels  g  and  h.  Heat  is  applied 
by  the  spirit  lamp  i.  The  water  for  the  bath  is  poured 
into  the  funnel  j,  its  temperature  is  indicated  by  the 
thermometer  k,  and  the  excess  escapes  at  the  overflow  /. 

To  make  a  test,  the  apparatus  is  placed  in  a  fairly 
dark  place,  so  that  the  size  of  the  test  flame  can  easily 
be  compared  with  the  bead/;  also,  the  flame  is  shielded 
from  all  air  currents.  The  water  bath  is  filled  with 
water  at  a  temperature  of  130  deg.  Fahr.,  and  the  oil 
to  be  tested  is  poured  into  the  cup  to  the  level  of  the 
gage  wire  b.  The  thermometer  c  is  next  inserted  and 


122  OIL  FUEL  FOR  STEAM  BOILERS 

the  spirit  lamp  i  is  lighted.  When  the  oil  reaches  a 
temperature  of  66  deg.  Fahr.,  the  test  flame  is  applied 
for  the  first  time,  and  again  after  that  every  time  the 
temperature  of  the  oil  has  increased  one  degree. 

To  insure  absolute  uniformity,  the  test  flame  is  ap- 
plied according  to  the  swinging  of  a  pendulum  24  in. 
long,  which  is  set  up  near  the  operator.  The  slide  d  is 
slowly  drawn  out  while  the  pendulum  is  making  three 
full  swings  in  both  directions  and  is  pushed  back  to  its 
original  position  during  the  fourth  swing.  When  the 
vapor  rising  from  the  oil  is  ignited  by  the  lamp  and 
gives  a  momentary  flash  of  blue  flame,  the  temperature 
registered  by  the  thermometer  c  should  be  noted.  This 
reading  is  the  flash  point  of  the  oil.  The  firing  point 
may  be  determined  next,  if  desired.  It  is  the  tempera- 
ture at  which  the  gases  are  given  off  in  such  quantity 
that  they  burn  continuously  when  ignited  by  the  test 
flame. 

If  the  oil  contains  water,  the  sample  to  be  used  for 
the  flash  test  should  be  freed  from  water  before  being 
put  into  the  tester;  for  as  little  as  i  per  cent,  of  water 
in  oil  will  cause  the  flame  to  be  extinguished  when  making 
a  flash  test. 

One  method  of  determining  the  percentage  of  water 
in  oil  is  to  make  use  of  the  affinity  of  petroleum  ether 
for  water.  A  weighed  sample  of  the  oil  to  be  tested  is 
placed  in  a  test  tube,  petroleum  ether  is  added,  the  two 
are  shaken  together  and  are  then  allowed  to  stand. 
The  ether,  with  the  water  it  has  taken  up  from  the  oil, 
will  collect  on  top  of  the  oil  and  should  be  decanted 
into  another  tube.  The  remaining  oil  should  again  be 


PURCHASE  OF  OIL  FUEL  123 

washed  with  petroleum  ether,  the  clear  solution  de- 
canted and  added  to  that  in  the  second  tube.  A  third 
'washing  may  be  performed  in  the  same  way. 

The  water  in  the  oil  is  removed  by  these  washings, 
being  carried  away  by  the  ether.  The  second  test  tube 
is  now  heated  to  a  temperature  of  from  100  deg.  to  140 
deg.  Fahr.,  when  the  petroleum  ether  boils  and  passes 
off,  leaving  the  water  in  the  bottom  of  the  test  tube. 
The  weight  of  this  water,  divided  by  the  weight  of  the 
original  sample  of  oil  and  multiplied  by  100,  gives  the 
percentage  of  water  in  the  oil. 

Another  method  is  to  weigh  the  sample  of  oil  and 
then  to  add  to  it  a  known  weight  of  plaster  of  Paris 
that  has  been  gently  ignited.  The  plaster  of  Paris  will 
take  up  all  the  water  in  the  oil,  after  which  it  should  be 
removed  and  washed  with  gasoline  to  remove  all  oil. 
It  should  then  be  dried  at  a  gentle  heat,  to  drive  off  the 
remaining  gasoline,  and  weighed.  The  increase  of 
weight  represents  the  water  absorbed  from  the  oil. 
Thus,  the  weight  of  the  original  sample  of  oil  and  the 
weight  of  the  moisture  are  known,  and  the  percentage 
of  moisture  may  readily  be  calculated.  A  good  oil  for 
fuel  should  not  contain  more  than  2  per  cent,  of  water. 

Oil  should  have  a  specific  gravity  of  from  0.85  to 
0.96  at  a  temperature  of  59  deg.  Fahr.,  and  should  be 
rejected  if  its  specific  gravity  is  0.97  or  more  at  that 
temperature.  It  should  not  contain  any  solid  or  semi- 
solid  bodies  and  should  flow  readily  at  ordinary  tem- 
peratures. A  good  test  for  fluidity  is  that  the  oil  shall 
flow  easily  through  10  ft.  of  4-in.  pipe  under  the  pres- 
sure due  to  a  head  of  i  ft.  of  oil.  It  should  not  freeze 


124  OIL  FUEL  FOR  STEAM  BOILERS 

or  become  top  sluggish  to  flow  at  32  deg.  Fahr.  The 
calorific  value  should  not  be  less  than  18,000  British 
thermal  units  per  pound.  As  to  cleanness  there  should 
be  no  more  than  a  trace  of  sand,  dirt  or  clay. 

The  oil  should  not  contain  more  than  i  per  cent,  of 
sulphur.  The  amount  present  in  the  oil  may  be  deter- 
mined in  the  following  manner:  A  sample  of  50  cc.  is 
put  in  a  flask  and  0.5  gram  of  sodium  bicarbonate  is 
added.  Heat  is  applied  to  the  mixture  and  it  is  dis- 
tilled at  the  rate  of  about  50  drops  per  minute  until 
about  45  cc.  has  been  driven  off.  The  residue  is  then 
placed  in  a  large  porcelain  dish  and  is  washed  several 
times  with  petroleum  ether.  The  ether  is  collected  from 
the  several  washings  and  evaporated.  About  half  a 
gram  of  sodium  is  next  added  in  small  pieces,  the  whole 
is  evaporated  over  a  small  flame  until  it  becomes  sirupy, 
and  then  is  ignited.  The  ignition  is  continued  until  the 
ash  is  quite  white,  ammonium  nitrate  being  added 
gradually  during  the  operation.  The  residue  is  treated 
with  very  dilute  hydrochloric  acid  and  barium  chloride 
is  added,  precipitating  barium  sulphate.  The  precipi- 
tate is  separated  by  filtration,  washed,  ignited,  and 
weighed,  and  the  amount  of  sulphur  contained  in  it 
is  calculated  by  multiplying  its  weight  by  0.13733. 
The  weight  of  sulphur  divided  by  the  weight  of  the 
original  sample  and  multiplied  by  100  gives  the  per- 
centage of  sulphur  in  the  oil. 

A  test  may  be  made  with  the  greatest  degree  of  accu- 
racy, yet  it  will  be  of  little  value  in  showing  the  com- 
position of  an  oil  unless  the  sample  that  is  tested  rep- 
resents properly  the  whole  quantity  of  oil.  Poor  methods 


PURCHASE  OF  OIL  FUEL  125 

of  taking  samples  or  mistakes  in  following  approved 
methods  may  result  in  unfair  and  misleading  results. 
For  this  reason  it  is  very  important  that  the  sampling 
be  done  correctly. 

The  manner  in  which  samples  are  taken  depends  on 
the  way  in  which  the  fuel  is  delivered.  If  the  oil  is 
brought  by  tank  wagon  or  tank  car  and  is  allowed  to 
flow  into  the  storage  tank  in  such  a  way  that  the  end 
of  the  discharge  pipe  is  accessible,  sampling  may  be 
done  with  a  dipper  holding  about  a  pint.  Immediately 
after  the  oil  begins  to  flow  into  the  storage  tank,  the 
dipper  should  be  filled  from  the  stream  of  oil  escaping 
at  the  end  of  the  pipe.  The  sample  thus  obtained 
should  be  poured  into  a  clean  vessel.  In  the  same  way 
other  samples  should  be  taken  at  equal  spaces  of  time 
during  the  emptying  of  the  car  or  wagon.  The  samples 
should  be  taken  often  enough  to  give  a  final  combined 
sample  of  at  least  a  gallon,  and  this  gallon  sample 
should  be  thoroughly  mixed  before  any  of  it  is  tested 
for  water  or  sulphur.  The  dipper  used  for  taking 
the  samples  should  always  be  filled  to  the  same  point, 
so  that  equal  amounts  will  be  taken  at  equal  intervals; 
but  if  the  first  dipperful  shows  water  in  the  oil,  it  should 
be  thrown  away  and  not  poured  into  the  receiving  vessel. 

In  case  the  end  of  the  discharge  pipe  cannot  be 
reached  for  sampling  with  a  dipper,  a  hole  may  be 
tapped  in  the  under  side  of  the  pipe  and  a  short  piece 
of  i/2-in.  pipe  and  a  valve  attached.  Then,  during  the 
whole  time  in  which  the  oil  is  being  discharged,  the 
valve  should  be  left  open  a  fixed  amount  and  a  con- 
tinuous sample  of  the  oil  thus  collected.  This  quantity 


126 


OIL  FUEL  FOR  STEAM  BOILERS 


should  be  thoroughly  mixed  in  a  clean  vessel  and  a 
sample  of  about  a  gallon  should  be  taken  from  it  for 
the  tests. 

In  case  the  oil  is  to  be  sampled  in  a  tank,  a  piece  of 
i-in.  pipe  somewhat  longer  than  the  depth  of  the  tank 
should  be  used,  as  shown  in  Fig.  62.  A  piece  of  wire  a 
is  attached  to  a  tapered  wooden  plug  b  of  sufficient  size 
to  close  the  end  of  the  pipe.  The  wire  is  carried  through 
the  pipe  and  has  a  loop  c  at  the  upper  end.  To  take 


c- 


FIGS.  62  and  63.  —  Sampling  pipe  and  sampling  bottle  on  rod. 

the  sample,  the  pipe  with  the  plug  hanging  below  it  is 
slowly  lowered  vertically  into  the  oil.  As  it  descends 
the  oil  rises  inside  it,  and  when  it  has  reached  the  bottom 
it  has  inclosed  a  column  of  oil  from  the  top  to  the  bottom. 
The  wire  is  now  pulled  up,  drawing  the  plug  into  the  lower 
end  of  the  pipe,  where  it  may  be  fixed  securely  by  bump- 
ing the  pipe  against  the  bottom  of  the  tank. 


PURCHASE  OF  OIL  FUEL  127 

The  pipe  is  now  drawn  out  and  emptied  into  a  vessel. 
The  oil  thus  obtained  is  a  representative  sample,  be- 
cause it  contains  oil  from  every  level  between  the  top 
and  the  bottom  of  the  tank;  thus,  even  if  the  oil  has 
separated  into  layers  of  different  specific  gravities,  the 
sample  includes  some  of  each.  Particular  care  should 
be  taken  to  lower  the  pipe  slowly,  so  that  the  oil  will  not 
be  stirred  up. 

If  it  is  deemed  advisable  to  take  samples  from  various 
parts  of  a  tank  instead  of  just  below  the  manhole,  a 
device  like  that  in  Fig.  63  may  be  used  to  advantage. 
It  consists  of  a  pole  a,  long  enough  to  reach  to  any  part 
of  the  tank,  to  which  is  fixed  a  bottle  b.  To  the  cork 
is  fastened  a  string  c  whose  other  end  is  attached  to  the 
upper  end  of  the  pole.  To  use  the  sampler,  the  bottle 
is  cleaned  and  loosely  corked.  Then  it  is  lowered  by  the 
pole  to  the  point  where  the  sample  is  to  be  taken  and  the 
cork  is  removed  by  a  pull  on  the  string.  The  bottle 
immediately  fills  with  oil,  is  drawn  out,  emptied,  and 
cleaned  for  the  next  sampling.  In  this  way  samples  are 
taken  from  various  points  symmetrically  located  in  the 
tank.  These  samples,  when  mixed  thoroughly,  form  a 
representative  sample. 

Sand  or  earthy  matter  in  oil  will  eventually  settle  to 
the  bottom  if  the  oil  is  allowed  to  stand  for  a  time  un- 
disturbed. Consequently,  to  determine  whether  an  oil 
contains  dirt,  a  cup  fixed  to  a  long  handle  may  be  used 
to  scrape  up  a  sample  along  the  bottom  of  the  tank.  If 
the  cupful  shows  a  considerable  amount  of  solid  matter, 
the  oil  is  dirty  and  may  prove  troublesome  to  use. 

There  has  been  considerable  speculation  as  to  what 


128  OIL  FUEL  FOR  STEAM  BOILERS 

effect  would  be  produced  on  the  tubes  and  plates  of 
steam  boilers  by  the  use  of  oil  fuel  containing  a  large  per- 
centage of  sulphur.  The  oil-trade  publication  Petro- 
leum^ in  a  brief  article  relating  specifically  to  Spindle 
Top  oil,  derived  from  the  Beaumont  field,  Texas,  state: 
that  the  results  in  many  tests  have  shown  that  "iron  01 
steel  flues  and  plates  are  not  more  seriously  affected  thar 
by  the  ordinary  coal  fuel.  Sulphur,  existing  in  a  fre< 
state,  or  as  sulphuretted  hydrogen  in  the  combustioi 
chamber,  has  both  hydrogen  and  oxygen  presented  to  it, 
with  which  it  will  unite  in  preference  and  will  not  act  cor- 
rosively on  the  metal  of  the  boiler.  It  is  besides  greatl} 
adulterated  by  the  volume  of  nitrogen,  oxygen  and  hy- 
drogen. In  many  of  the  best  grades  of  bituminous 
coal,  the  sulphur  varies  from  i  per  cent,  in  the  best  to 
31/2  per  cent.  Even  coal  containing  as  much  as  4  to  5 
per  cent,  of  sulphur  is  used  without  injury  to  the  boiler 
proper,  however  much  the  grate  bars  may  suffer.  The 
percentage  of  sulphur — actually  not  more  than  1.33  per 
cent. — is  lower  than  that  found  in  some  descriptions  of 
coal  used  as  fuel,  and  cannot  be  regarded  as  disqualify- 
ing the  oil  for  advantageous  employment  in  the  furnaces 
of  steam  boilers." 


CHAPTER  XIII 

ADVANTAGES  AND  DISADVANTAGES  OF  OIL  FUEL 

Oil  as  a  fuel  has  several  well-defined  advantages  over 
:coal  and  other  solid  fuels.  Perhaps  the  most  apparent 
of  these  is  the  ease  and  rapidity  with  which  the  rate  of 
firing  may  be  changed.  In  a  plant  in  which  regula- 
tion is  carried  out  ^by  hand,  the  simple  operation  of 
turning  a  valve  or  a  cock  suffices  to  increase  or  de- 
crease the  flow  of  oil  to  the  burners,  whereas  if  auto- 
matic regulation  is  used  the  ratio  of  steam  to  oil  and  of 
oil  to  load  are  all  taken  care  of  by  the  automatic  de- 
vices. The  result  of  this  action  is  that  the  rate  of  com- 
bustion follows  the  load  so  closely  that  the  steam  pres- 
sure can  be  kept  very  nearly  uniform.  In  addition  to 
this  feature,  it  is  possible  to  extinguish  the  fires  almost 
instantly,  in  case  of  accident  to  some  part  of  the  plant, 
and  thus  prevent  further  disaster. 

Inasmuch  as  the  rate  of  firing  can  be  increased  from 
almost  nothing  to  the  maximum  in  the  short  space  .of 
time  required  to  open  a  valve,  the  response  to  a  sud- 
den increase  of  load  on  the  boiler  is  much  quicker  with 
oil  fuel  than  with  coal.  For  with  coal  firing,  an  in- 
crease of  load  is  met  by  throwing  greater  quantities  of 
fuel  on  the  grates,  the  immediate  result  of  which  is  to 
chill  the  fire  and  reduce  the  amount  of  heat  liberated. 
After  the  fresh  fuel  has  become  heated  and  ignited  it 
9  129 


130  OIL  FUEL  FOR  STEAM  BOILERS 

gives  off  increased  heat,  but  this  requires  appreciable 
time.  With  oil,  the  generation  of  heat  is  proportional 
to  the  amount  of  oil  fed  and  is  simultaneous  with  the 
injection  of  the  oil  into  the  furnace.  The  advantage  of 
this  in  a  plant  that  is  subject  to  frequent  and  wide 
variations  in  load  must  be  apparent. 

In  the  hands  of  an  ignorant  and  untrained  fireman, 
however,  this  ease  of  control  may  prove  to  be  a  source 
of  trouble  and  danger.  For,  in  getting  up  steam  from 
a  cold  boiler  or  in  bringing  a  banked  boiler  into  normal 
working  condition  he  may  force  the  firing  to  such  an 
extent  as  to  burn  the  plates  or  tubes  and  render  the 
boiler  unsafe. 

An  increase  of  steaming  capacity  is  made  possible  by 
a  change  from  solid  to  liquid  fuel,  provided,  of  course, 
that  reasonable  precautions  are  taken  to  arrange  the 
furnace  for  the  economical  use  of  oil.  The  increase  of 
capacity  is  attributable  to  a  number  of  causes.  In  the 
first  place,  oil  has  a  greater  calorific  value  per  pound 
than  coal.  A  pound  of  high-grade  steam  coal  will  yield 
13,500  British  thermal  units  and  a  pound  of  oil  of  aver- 
age quality  will  contain  18,600  British  thermal  units. 
The  difference,  5,100  British  thermal  units,  represents 
38  per  cent,  of  the  heating  value  of  the  coal;  therefore, 
it  may  safely  be  stated  that  oil  has  from  30  to  35  per 
cent,  greater  calorific  value  than  coal. 

When  burned  in  the  furnace,  a  greater  percentage  of 
the  heating  value  of  the  oil  is  utilized  than  in  the  case 
of  coal.  In  the  first  place,  a  smaller  excess  of  air  is 
required  for  oil,  because  the  mixing  with  the  fuel  is 
more  thorough.  The  combustion  is  therefore  more 


ADVANTAGES  AND  DISADVANTAGES  OF  OIL  FUEL  131 

efficient,  a  greater  percentage  of  the  available  heat  is 
developed,  and  the  temperature  of  the  furnace  is  higher 
than  with  coal  because  the  weight  of  gases  produced  by 
combustion  is  smaller.  As  a  consequence,  these  gases 
give  up  more  heat  to  the  boiler  than  do  the  products 
of  combustion  of  coal. 

The  heating  surfaces  of  a  properly  managed  oil- 
burning  boiler  are  cleaner  than  those  of  a  coal-burning 
boiler  because  the  improved  furnace  conditions  lessen 
the  formation  of  soot,  and  there  are  no  solid  particles 
to  be  carried  into  the  tubes  by  the  draft.  This  renders 
the  transfer  of  heat  from  the  gases  to  the  water  more 
rapid  and  raises  the  evaporative  efficiency.  Again,  with 
oil  fuel  there  is  no  necessity  for  opening  the  fire-doors 
at  frequent  intervals,  as  is  done  in  the  hand  firing  of 
coal;  therefore,  the  furnace  conditions  are  kept  more 
nearly  uniform,  there  is  a  better  distribution  of  the  heat 
generated,  and  the  stresses  due  to  the  cooling  effect  of 
large  volumes  of  cold  air  admitted  to  the  furnace  are 
avoided. 

There  are  just  two  fundamental  ways  of  increasing 
the  efficiency  of  a  boiler,  and  they  are  to  increase  the 
amount  of  heat  absorbed  and  to  reduce  the  amount  of 
heat  thrown  away.  With  oil  as  a  fuel,  less  heat  is  used 
to  raise  the  temperature  of  the  excess  air  and  more 
heat  is  transferred  to  the  water.  The  net  result  of 
these  two  actions  is  that  a  smaller  percentage  of  heat 
escapes  up  the  chimney  in  the  gases,  and  so  the  efficiency 
is  increased. 

Because  of  the  slight  excess  of  air  that  is  required 
in  an  oil-burning  installation  the  weight  of  gases  formed 


132  OIL  FUEL  FOR  STEAM  BOILERS 

per  pound  of  oil  is  less  than  the  weight  resulting  from 
the  combustion  of  a  pound  of  coal,  and  a  chimney  of 
smaller  capacity  can  be  used.  Again,  the  draft  needed 
for  oil  fuel  is  from  one-tenth  to  one-half  that  necessary 
for  the  efficient  burning  of  coal;  consequently,  the 
height  of  the  chimney  need  not  be  so  great  when  oil  is 
used.  In  the  case  of  a  plant  converted  from  coal  burn- 
ing to  oil  burning,  the  existing  chimney  would  be  used 
without  alteration,  and  this  particular  advantage  would 
be  of  no  immediate  benefit;  but  in  the  case  of  a  new 
plant  designed  for  oil  fuel  the  cost  of  chimney  construc- 
tion would  be  considerably  less  than  for  a  coal-burning 
plant  of  equal  capacity,  because  of  the  reduced  height 
and  diameter  of  the  chimney. 

Another  striking  advantage  of  oil  as  a  fuel  is  the 
lessening  of  manual  labor  by  its  use.  Instead  of  trans- 
porting the  fuel  from  the  storage  bins  in  trucks  or 
barrows  and  feeding  it  to  the  furnaces  with  scoops, 
as  in  the  case  of  coal,  the  oil  is  drawn  from  the  storage 
tanks  and  sent  to  the  burners  by  steam  pumps.  As  a 
consequence,  the  number  of  firemen  may  be  reduced  to 
one-half  or  even  one-fifth  of  the  original  number,  de- 
pending on  the  size  of  the  plant  and  its  arrangement. 
Even  a  coal-burning  plant  equipped  with  conveyors  and 
other  mechanical  devices  requires  far  more  power  for 
handling  the  fuel  than  does  an  oil-burning  plant  of 
equal  capacity.  Moreover,  oil  can  be  pumped  through 
pipes  to  far  greater  distances  and  at  much  smaller  ex- 
pense than  would  be  possible  in  the  case  of  coal.  For 
example,  take  the  case  of  a  plant  situated  near  a  river 
or  other  deep  waterway,  to  which  fuel  could  be  brought 


ADVANTAGES  AND  DISADVANTAGES  OF  OIL  FUEL  133 

by  barges  or  steamers.  If  coal  were  used,  expensive 
machinery  would  be  required  to  transfer  it  from  the 
barges  to  the  plant  over  the  intervening  distance;  but 
if  oil  were  the  fuel,  all  that  would  be  required  would 
be  a  pipe  line  between  the  plant  and  the  edge  of  the 
river,  as  compared  with  the  structural  work  required 
to  carry  the  coal-handling  machinery. 

In  the  matter  of  storage  space  required,  oil  has  a 
vast  advantage  over  coal.  Oil  possesses  about  one-third 
more  heating  value  than  an  equal  weight  of  coal  and  a 
pound  of  oil  occupies  about  three-fifths  of  the  space 
required  for  a  pound  of  coal;  therefore,  the  heating 
value  of  the  oil  that  can  be  stored  in  a  given  space  is 
almost  50  per  cent,  greater  than  that  of  the  coal  that 
could  be  put  in  the  same  space.  To  put  it  in  another 
way,  the  storage  space  required  when  oil  is  used  as  a, 
fuel  is  only  about  two-thirds  of  that  for  coal,  assuming 
the  same  boiler  horsepower  in  both  cases. 

The  ashes  produced  in  the  burning  of  coal  must  be 
removed  periodically.  The  handling  of  these  ashes  in 
the  boiler  room  produces  dust,  and  the  whole  process 
of  removal  involves  expense.  Oil  produces  no  ashes 
and  no  dust,  and,  if  properly  burned,  no  soot.  The  re- 
sult is  that  there  is  no  expense  for  removal  of  ashes, 
the  wear  and  tear  on  the  pumps  in  the  boiler  room  is 
reduced  by  the  absence  of  dust,  and  the  tubes  and  sur- 
faces of  the  boiler  remain  clean  for  longer  periods  than 
when  coal  is  used.  This  last  condition  lessens  the  fre- 
quency of  cleaning  the  tubes  and  so  reduces  labor  and 
expense. 

The  apparatus  used  in  connection  with  oil  burning  is 


134  OIL  FUEL  FOR  STEAM  BOILERS 

simple  and  is  not  apt  to  get  out  of  order;  therefore,  the 
cost  of  maintenance  is  not  great.  Burners  may  wear, 
owing  to  erosion  by  the  oil  and  steam,  or  may  warp 
under  the  effect  of  the  intense  heat  so  as  to  require 
renewal;  but  the  absence  of  moving  or  sliding  parts 
reduces  the  repair  bills  to  a  minimum.  There  are  no 
grates  to  be  replaced,  and  no  firing  tools  are  used,  so 
that  damage  to  the  bridge  wall  or  to  the  furnace  lining 
through  the  careless  use  of  tools  is  wholly  avoided. 

It  is  well  known  that  coal,  when  stored  for  any  length 
of  time,  deteriorates  in  heating  value  because  of  slow 
oxidation  and  the  escape  of  hydrocarbons;  but  oil  may 
be  stored  for  long  periods  in  properly  ventilated  tanks 
without  losing  appreciably  in  its  heating  value. 

Again,  there  is  the  matter  of  smokelessness  to  be 
considered.  By  reason  of  the  efficient  combustion  that 
may  be  obtained,  oil  can  be  burned  without  smoke;  so 
that,  in  a  city  in  which  the  production  of  smoke  by 
manufacturing  plants  is  punished  by  fines,  the  use  of 
oil  fuel  may  be  the  means  of  solving  a  trying  problem. 

One  of  the  chief  disadvantages  attending  the  use  of 
oil  fuel  is  imposed  by  the  regulations  of  insurance  com- 
panies. To  protect  the  plant  from  fire  that  might  occur 
from  the  ignition  of  the  inflammable  oil,  it  is  required 
that  the  storage  tank  shall  be  30  ft.  from  the  nearest 
building  and  2  ft.  below  the  surface  of  the  ground,  or 
200  ft.  from  inflammable  property  if  located  above 
ground.  It  may  be  difficult  to  comply  with  these  regu- 
lations if  the  ground  surrounding  a  plant  is  in  great 
demand  or  is  already  occupied. 

Another  disadvantage  of  oil  is  the  inflammability  of 


ADVANTAGES  AND  DISADVANTAGES  OF  OIL  FUEL  135 

the  gases  given  off  from  it.  The  danger  of  explosion 
of  these  gases  and  the  subsequent  ignition  of  the  oil, 
however,  become  of  small  importance  if  the  oil  used  has 
a  flash  point  of  140  deg.  Fahr.  or  more,  and  if  reasonable 
precautions  are  taken  in  storing  and  using  it. 

If  the  boiler  feed-water  contains  a  large  percentage 
of  scale-forming  material,  the  use  of  oil  fuel  may  entail 
increased  expense  for  repairs  and  tube  renewals;  for 
the  intense  heat  generated  in  an  oil-burning  furnace  is 
apt  to  cause  more  rapid  deposit  of  scale  and  result  in  a 
greater  number  of  burned  tubes  and  plates  than  with  a 
coal  fire. 


CHAPTER  XIV 
PERFORMANCES  or  OIL-BURNING  BOILERS 

The  evaporation  of  a  pound  of  water  at  212  deg. 
Fahr.  into  steam  at  the  same  temperature  requires 
970.4  British  thermal  units;  therefore,  if  all  the  heat  in  a 
pound  of  oil  containing  18,600  British  thermal  units 
could  be  used  in  evaporating  water,  it  would  convert 
18,600  -r-  970.4  =  19.2  Ib.  of  water  at  212  deg.  Fahr. 
into  steam.  Under  the  same  conditions,  a  pound  of  coal 
having  a  calorific  value  of  13,500  British  thermal  units 
would  evaporate  13.9  Ib.  of  water. 

Such  results  as  the  foregoing,  however,  are  not  at- 
tainable in  practice,  because  some  of  the  heat  in  the  fuel 
is  spent  otherwise  than  in  heating  the  water  in  the  boiler. 
For  example,  part  of  it  escapes  up  the  chimney  in  the 
flue  gases,  which  leave  the  boiler  at  a  temperature  of 
400  deg.  Fahr.  or  more,  and  some  of  it  is  lost  by  radiation. 
The  result  is  that  only  a  part  of  the  heat  content  of  the 
fuel  is  usefully  employed  in  converting  water  into 
steam.  The  ratio  of  the  heat  actually  used  in  evapo- 
rating water  to  the  amount  supplied  to  the  furnace  in 
the  fuel  in  the  same  time  is  the  net  boiler  efficiency. 

The  boiler  efficiency  varies  considerably,  even  in  the 
case  of  boilers  of  the  same  size  and  make,  and  in  the  case 
of  the  same  boiler  operated  under  different  conditions. 
It  depends  on  such  factors  as  the  quality  of  combustion^ 

136 


PERFORMANCES  OF  OIL-BURNING  BOILERS     137 


TABLE  V. — RESULTS  OF  TESTS  ON  OIL-BURNING  BOILERS 


Designation  of  tests  

A 

B 

C 

Duration  of  test  hr                    

7 

8 

4 

Steam  pressure  Ib 

184.8 

178."? 

142 

Superheat  deg.  Fahr  

98.3 

1  60 

83 

Feed-  water  temperature,  deg.  Fahr  
Barometer  in   of  mercury 

93-7 
20   07 

165 

3O.4 

119.6 

Boiler-room  temperature,  deg.  Fahr  

86.2 

75 

82 

Flue-gas  temperature,  deg.  Fahr  
Draft  in  ashpit  in 

434-5 
0.084 

384 

O.O2 

488 

Draft  in  furnace  in 

o  062 

o.  15 

Carbon  dioxide  per  cent  

13.2 

13.05 

13-25 

Oxygen  per  cent                        

•2      I 

5.15 

Excess  of  air  per  cent 

21     2 

18 

Total  water  evaporated,  Ib  

147,351 

156,974 

82,317 

Evap.  from  and  at  212  deg.  Fahr.,  Ib  
Steam  used  by  burners,  Ib.  per  hr  
Steam  used  by  burners  per  cent  of  total 

182,771 
568 
2    I< 

186,799 

97,694 

377 
i  .54 

Steam  pressure  to  burners  Ib 

122    2 

Oil  pressure  to  burners   Ib 

Si  6 

78 

Oil  temperature  at  burners,  deg.  Fahr  
Specific  gravity  of  oil  at  60  deg.  Fahr  
IVloisture  in  oil  per  cent 

J37-9 
0.9.776 

O    ZA. 

128 
0.9700 

I  .  2 

97 

Heat  value  of  oil  as  fired,  B.T.U  
Heat  value  of  oil  corrected  B.T.U  

18,184 
l8,28l 

iSxis 

17,425 

Oil  fired  per  hr    Ib 

I  74.  ^ 

1,4.80 

1,672 

Oil  fired  per  hr.   corrected,  Ib  

1,771; 

1,462 

Evap.  per  sq.  ft.  of  heating  surface,  Ib.  .  .  . 
Rated  horsepower  of  boiler 

4-32 
604 

3.62 

64.1; 

3.60 
595 

Boiler  horsepower  developed       

756.8 

676.7 

707  .  9 

Evaporation  from  and  at  /  as  fired,  Ib. 
21  2  deg.  Fahr.  per  Ib.  of  oil.  1  corrected,  Ib. 
Boiler  efficiency,  per  cent  

I5-I5 
I5-23 
80.47 

15-775 

I5-96? 
8s.  60 

14.61 
80.97 

138  OIL  FUEL  FOR  STEAM  BOILERS 

eakage  of  air  into  the  furnace  or  passages,  loss  of  heat, 
and  direct  loss  of  fuel.  In  a  coal-burning  boiler,  the 
efficiency  will  not  exceed  75  per  cent,  very  often.  If  it 
is  between  70  and  75  per  cent.,  the  performance  may  be 
considered  very  satisfactory;  but  if  it  falls  below  60  per 
cent.,  efforts  should  be  made  to  determine  the  source  of 
loss  and  remedy  the  defect. 

In  the  case  of  boilers  using  oil  fuel,  a  much  higher  boiler 
efficiency  may  be  expected,  because  of  the  increased 
efficiency  of  combustion.  There  are  records  of  numerous 
tests  showing  efficiencies  of  more  than  80  per  cent.,  and 
at  least  one  test  came  to  within  a  very  small  fraction 
of  84  per  cent.  In  fact,  if  the  efficiency  of  an  oil-burning 
boiler  falls  below  75  per  cent.,  an  examination  should  be 
made  to  discover  the  cause  of  the  lowered  efficiency. 

Data  on  the  performances  of  steam  boilers  burning 
oil  fuel  are  given  in  Table  V.  The  values  given  in  the 
column  headed  A  represent  the  average  of  seven  tests 
made  in  1907  on  a  Babcock  &  Wilcox  boiler  with  Ham- 
mel  burners.  Several  features  of  the  tests  may  be  pointed 
out  as  contributing  to  the  excellent  economy  secured. 
The  temperature  of  the  escaping  flue  gases  was  reduced 
to  434.5  deg.  Fahr.,  the  amount  of  carbon  dioxide  in  the 
flue  gases  was  13.2  per  cent.,  and  the  excess  of  air 
amounted  to  only  21.2  per  cent.  .  The  oil  used  was  a 
crude  oil  from  the  Los  Angeles  field,  and  the  ashpit 
doors  were  left  wide  open  during  the  tests,  the  draft 
being  regulated  by  the  damper. 

The  results  shown  in  column  B  were  obtained  in  1911 
from  a  single  test  of  a  Parker  boiler  fitted  with  a  tubular 
inside-mixing  slot  burner.  The  extremely  high  efficiency 


PERFORMANCES  OF  OIL-BURNING  BOILERS    139 

of  83.69  per  cent,  may  be  attributed  to  excellent  combus- 
tion and  a  low  flue-gas  temperature. 

These  same  features  stand  out  prominently  in  the  data 
shown  in  column  C,  which  were  obtained  in  1907  from 
a  single  test  of  a  Babcock  &  Wilcox  boiler  with  a 
Peabody  furnace  and  a  Peabody  burner  directed  toward 
the  front  of  the  boiler.  The  small  amount  of  steam 
used  by  the  burners — 1.54  per  cent,  of  the  total  steam 
generated — is  an  excellent  showing. 

These  three  sets  of  data  show  unusually  good  per- 
formances, but  they  likewise  indicate  the  results  that 
can  be  obtained  by  the  careful  operation  of  oil-burn- 
ing equipment  well  designed  and  arranged. 


INDEX 

(Numbers  refer  to  pages) 


Abel  tester,  119,  120 
Advantages  of  oil  fuel,  129 
Air,  excess  of,  104,  105 

preheating  of,  in 

required  for  combustion,  104 

supply,  regulation  of,  114 
American  fuel  oils,  12,  13 
Atomizer,  mechanical,  22,  38 
Atomizing,  methods  of,  20 

object  of,  17 

steam  required  for,  26 
Automatic  regulation,  112,  113 


B 


Babcock  &  Wilcox  boiler,  fur- 
nace for,  69,  71,  78 
Banking  fires  with  oil,  77,  78 
Baume  hydrometer,  6 
Best  burner,  32 
Boiler  efficiency  with  oil  fuel, 

138 

fired  from  rear,  71,  75,  78 
furnace  for  Babcock  &  Wil- 
cox, 69,  71,  78 
furnace  for  Heine,  73 
furnace     for    return-tubular, 

66,  67,  68 
furnace  for  Stirling,  74,  75,  76 


Booth  burner,  30 
Burner,  Best,  32 

Booth,  30 

capacity  of,  84,  85 

chamber,  25 

drooling,  24 

erosion  of,  27,  35,  42 

erratic  action  of,  in 

Gem,  28,  29 

Hammel,  34 

injector,  25 

inside-mixing,  24 

inside- mixing  slot,  42 

Kirk  wood,  36,  40 

Koerting,  38 

location  of,  85 

outside-mixing,  24 

outside-mixing  slot,  41 

Parson,  29 

projector,  24 

regulation  of,  in,  112 

requisities  of  good,  27 
Burners,  number  required,  84, 

85 

piping  for,  80,  81 
By-pass    for    cleaning     burner, 


Calorific  value  of  oil,  5,  6 


141 


142 


INDEX 


Capacity  of  burner,  84,  85 

of  oil  tank,  100,  101 

of  storage  tank,  91 
Centrifugal  spray  nozzle,  38 
Chamber  burner,  25 
Cleaning  oil  by  settling,  44 
Coal    used    with    oil    fuel,    77, 

78 

Cold  air,  effect  of,  in 
Color  of  fire,  no 
Combustion,    air   required   for, 

104 

effect  of  steam  on,  107 
efficiency  of,  102 
of  oil  fuel,  102 
Correction  of  specific  gravity, 

10 
Crude  oil,  4 


Decomposition  of  oil,  63 
Density  of  oil,  6,  7 
Dirt  in  oil,  44 

Disadvantages  of  oil  fuel,  134 
Distillation  of  petroleum,  4 
Draft  required  for  oil,  113 
Drooling  burner,  24 


Evaporative  tests  with  oil,  136, 

I37 
Excess  of  air,  104,  105 


Filling  storage  tank,  92 
Fire,  color  of,  no 

smothering  oil,  98,  115 

starting  oil,  108,  109 
Firebrick,  76 
Firing  point,  122 
Flash  point,  118 

finding,  121,  122 
Flooding,  prevention  of,  57 
Fluidity  of  oil,  123 
Fuel,  combustion  of  oil,  102 
Fuel  oils,  4,  12,  13 
Furnace  for  Bab  cock  &  Wilcox 
boiler,  69,  71,  78 

for  Heine  boiler,  73 

for  return-tubular  boiler,  66, 
67,68 

for    Stirling    boiler,    74,    75, 
76 

lining,  76 

volume,  102,  103 
Furnaces  for  oil  fuel,  18 


Efficiency  of  oil-burning  boiler, 

138 

of  combustion,  102 
Emptying  tank  car,  92 
Erosion  of  burner,  27,  35,  42 


Gem  burner,  28,  29 


H 


Hammel  burner,  34 


INDEX 


143 


Hand  regulation,  in,  112 
Heat  value  of  oil,  5,  6 
Heater,  oil,  59,  61,  62 
Heating  oil,  object  of,  63 
Height  of  oil  column,  56 
Heine  boiler,  furnace  for,  73 
Hydrometer,  Baume,  6 


I 


Indicator,  tank,  95,  96 
Injector  burner,  25 
Inside-mixing  burner,  24,  42 


Kirk  wood  burner,  36,  40 
Koerting  burner,  38 


Lining  of  furnace,  76 
Location  of  burner,  85 
of  storage  tank,  91,  92 

M 

Mamagement     of     oil-burning 

plant,  108 

Mechanical  atomizer,  22,  38 
Moisture  in  steam,  85 


N 


Number  of  burners  required,  84, 

85 


O 


Oil  burners,  piping  for,  80,  81 
calorific  value  of,  5,  6 
crude,  4 

decomposition  of,  63 
density  of,  6,  7 
fields  of  United  States,  2 
finding  temperature  of,  64 
fire,  restarting,  115 
fire,  shutting  down,  115 
fire-smothering,  98,  115 
fuel,  combustion  of,  102 
fuel  for  banking  fires,  77,  78 
fuel  for  peak  loads,  77,  78 
fuel,  purchase  of,  117 
fuel  used  with  coal,  77,  78 
fuel,  water  in,  122,  123 
heater,  59,  61,  62 
object  of  heating,  63 
pressure,    amount     required, 

56 

pressure,  necessity  for,  56 
pressure,  pump  for,  58 
pump,  54 

sand  and  dirt  in,  44 
specific  gravity  of,  7 
Oils,  American  fuel,  12,  13 
Outside-mixing  burner,  24,  41 


Parson  burner,  29 
Peak  loads,  oil  for,  77,  78 
Petroleum,  2,  3 
distillation  of,  4 


144 


INDEX 


Piping  for  oil  burners,  80,  81 
Preheating  of  air,  1 1 1 
Pressure,  necessity  for  oil,  56 

pump  for  oil,  58 

usual  oil,  56 
Projector  burner,  24 
Pump,  oil,  54 
Purchase  of  oil  fuel,  117 


Regulating  cock  for  oil,  82 

valve  for  oil,  83,  84 
Regulation  of  air  supply,  114 

of  burner,  in,  112 
Restarting  oil  fire,  115 
Return-tubular   boiler,   furnace 

for,  66,  67,  68 
Roaring  in  furnace,  1 1 1 


Safety  device  for  draining  stand- 

pipe,  55 
Sampling  oil  with  bottle,  127 

oil  with  dipper,  125 

oil  with  pipe,  126 
Sand  in  oil,  44,  127 
San  Joaquin  valley  oils,  14 
Shutting  down  oil  fire,  115 
Size  of  strainer  openings,  45 
Slot  burner,  inside-mixing,  42 

burner,  outside-mixing,  41 
Smoke,  19,  105,  106 
Smothering  oil  fire,  98,  115 
Soot,  105,  106 


Specific  gravity,  correction  of, 
10 

gravity  of  oil,  7 
Standpipe  for  oil  pressure,  55 

safety    device    for    draining, 

55 

Starting  oil  fire,  108,  109 
Steam,    effect    on    combustion, 
107 

moisture  in,  85 

required  for  atomizing,  26 

superheated,  85 

used  by  burner,  86,  87 
Stirling  boiler,  furnace  for,  74, 

75,  ?6 
Storage  space  for  oil,  133 

tank,  90 

tank,  capacity  of,  91 

tank,  filling,  92 

tank,  location  of,  91,  92 
Strainer,  basket,  49 

for  suction  pipe,  48 

Koerting,  50 

materials  for,  45 

perforated  metal,  49,  52 

piping  for,  46 

requirements  of  good,  47 

simple  form  of,  46 

size  of  openings  in,  45 

T-fitting,  48 

Sulphur  in  oil,  3,  124,  128 
Superheated  steam,  85 


Tank,  capacity  of  oil,  91 


INDEX  145 

Tank  car,  emptying,  92  V 

filling  storage,  92 

indicator,  95,  96  Vent  pipe  for  tank,  94,  95 

location  of  storage,  91,  92  Volume  of  furnace,  102,  103 

size  of  storage,  89 

storage,  90  W 

Telltale,  95 
Temperature  of  oil,  64  Water  in  oil  fuel,  122,  123 


BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


NOV 


1934 


NOV   21   1934 


*r.?< 


> 


YB   15440 


302931 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


